Conviction by Contradiction

""You don't like the way I phrased an answer, what kind of evidence is that?""

- The guy who did it, Monk, "Mr. Monk Fights City Hall"

The classic whodunit challenges the viewer to solve the crime along with the detective. Since the viewer isn't a professional, the crime has to be set up so that the solution doesn't rely on skills only a professional criminologist would have. These mysteries often work by reducing the crime to a logic puzzle: you solve the mystery by finding the fact that doesn't fit.

The problem with this is the "solution" at the back of the book doesn't give the perp a chance to offer a perfectly reasonable explanation.

Real crimes aren't logic puzzles and mere factual inconsistencies aren't a substitute for hard evidence. Poking holes in a suspect's story might push a jury over the edge, but it's not going to convince them by itself. You might be able to Pull the Thread, but on its own, proving that the suspect lied about something doesn't prove he committed the crime (especially if he has a Big Secret). At best, this kind of logic game can be used during Perp Sweating to get a confession. At worst, Detective Brown will arrest the perp immediately, but Perry Mason wouldn't even break a sweat getting an acquittal from that.

The level to which this trope is justified depends on what the contradiction is being used to prove. A novel explanation for a baffling set of circumstances can give the police a new avenue for their investigation. Inconsistencies in a person's story may not enough to prove they committed a crime but it can prove they lied to the police and that would be enough to pursue warrants or get them on a charge such as obstruction of justice that could lead to other more tangible forms of evidence. However, in countries where the accused is innocent until proven guilty, a "logical flaw" in the perp's alibi will make for a strong circumstantial case at best, but it far from meets the standard of proof of "guilty beyond a reasonable doubt".

For this reason, most examples realistically focus on the investigative side, where the contradiction satisfies the significantly lower standard of proof required to arrest someone, without dwelling on the Fridge Horror of whether the merits of the case meet the "Prima facie" burden required to convict them. However, some stories allow the Hand Wave that the contradiction inevitably leads to the find of real evidence. As such, Justifying Edits are not necessary, and points that have these still fit if the actual "conviction" is simply tacked on to the end of the story.

On the other hand, a logical inconsistency in the testimony of a key witness for the prosecution can blow a hole in the case. If the witness claims to have seen something they could not possibly have seen, or could not possibly have seen the way they claim to have seen it, it puts the testimony in doubt. Which creates exactly the kind of "reasonable doubt" that allows the accused to walk. In short, casting doubt on the prosecution's case doesn't require proving someone else did it or that you're innocent; only that the case against you is questionable enough to think you might not have done it.

In most stories involving teenage perpetrators, the crimes are rather minor and the solution has them immediately confess as a result of being "trapped by his/her lie." It's rather more Egregious when it's shown to work against full-fledged adults under suspicion of serious felony charges who are assumed to know their rights and to remain silent or ask for a lawyer when the police suspect them of a crime. But then again--

See also Conviction By Counterfactual Clue, which is when the "flaw" found to prove the suspect's guilt is simply erroneous. This overlaps with Hyper Awareness -- sometimes it's just hyper-awareness taken too far, to the point of noticing details that logically shouldn't even be noteworthy. Can lead to a minor Inferred Holocaust, if logic dictates that the supposedly happy ending will lead to either a guilty character escaping or an innocent one being convicted. These types of inferences often run afoul of Hanlon's Razor, blaming every flaw or contradiction on lies and conspiracy rather than, say, faulty memory or panic.

Compare I Never Said It Was Poison, where the suspect demonstrates knowledge of a detail or two they shouldn't.

This gets particularly egregious when the story contains perfectly good alternative clues, but the flimsy one was chosen as The Clue.

Encyclopedia Brown

 * This has happened so often in Encyclopedia Brown shorts that the former Trope Name was Bugs Meany Is Gonna Walk.
 * A "witness" trying to frame a boy for the theft of a pocket knife claims the boy took the knife with his right hand, and put it in his pocket while running away. He is found innocent because he has a cast on his left hand and the knife was found in his left pants pocket (planted there by the "witness") and (according to the answers section at least) it's impossible to put a pocket knife in your left pants pocket with your right hand while running. Leaving aside that Encyclopedia was assuming an impossibility out of a difficult, and highly improbable physical stunt, the mere likelihood of him putting the knife in his left pocket after he'd stopped running never occurred to him. Of course, since the inconsistency here is being used on the defendant's behalf to create reasonable doubt, it's more valid than most of the other examples on this page.
 * The page quote for Conviction By Counterfactual Clue comes from a different mystery that used the same trick -- a stolen key (or some such thing) was found in the right pants-pocket of a man with a cast on his right arm, which "proves" it was planted. Never mind that it's not that difficult to put your left hand in your right pocket; the pants were found in a locker after he'd changed clothes and it's entirely possible that he put something in the pocket after taking off his pants.
 * The perp claims to have been out of town during the crime, but knows details about some contemporaneous local event. (Because, clearly, he never talks to anyone about local events or reads newspapers)
 * The perp claims to have seen something by moonlight on a night when there was no moon. It's entirely possible that the perp saw the incident by another ambient source of light and simply assumed it was moonlight. Interestingly, Abraham Lincoln got an acquittal in a case in exactly this manner, though in his case it was used to show that, without moonlight, it would have been impossible to see something 150 ft away at night in 1858.
 * A boy blows his fake alibi by tracing a shirt pocket on the wrong side of his chest. This is perfectly understandable, since everyone is accustomed to seeing images of themselves in the mirror, where left and right are flipped.
 * A man accused of committing a robbery is being interrogated in the crime scene and claims he has never been there before. Shortly afterward, he says, "When you brought me back here, did I resist?" to the police officer. Since he couldn't be brought back if he had never been there before, the man is guilty. First of all, the term "back" doesn't have to mean "return." It can simply indicate distance or location, shown in common phrases such as, "He's from back east." You can also say you're taking someone "back" somewhere if you've already been there. The all-too-common example would be asking a stranger, "Want to go back to my place?"
 * A perp claims to have been on the bottom floor of a building when the crime was committed, yet when he went to the elevator, he pressed the "up button." Encyclopedia deduces that the perp was probably not on the very bottom floor, because the perp wouldn't have had to distinguish the button as the "up button" because there wouldn't have been a "down button." Of course, an "up button" is always an "up button" whether or not there's a "down button" along with it. The actual name for them is "call button", but it's rarely used outside of technical and legal documentation. Besides, plenty of call buttons still have the appropriate arrow on them even when they're on the top and bottom floors.
 * The perp tells someone he's hidden a $2 note between an odd and even page of a book that are normally on opposite sides of a leaf if the book is read left to right. It might be possible that the book had a typo, breaks the tradition, had its pages printed out of order, or the perp simply misremembered the book pages. Either way, this is one of the mysteries that has an obvious answer of simply looking at the book or checking out a copy of it to prove he's lying but Brown insists on over-thinking the solution.
 * Sometimes the book isn't even known; in one instance the perp said he put the bill between two pages of 'the grey book on the table' in a library, and the book was assumed to be reshelved by the time the detective arrived (and couldn't find it). This makes it even less likely that the detective would somehow know the page ordering in that book.
 * A stolen rare coin is found inside Bugs Meany's hot dog. How did Encyclopedia know where to find it? Because he saw Bugs spread mustard on top of the sauerkraut, and "no one who likes hot dogs does that." Admittedly, it is a pretty messy way to go about things (similar to trying to spread jelly on top of peanut butter), but c'mon. Interestingly, the story effectively admits Bugs would have walked if he'd been willing to finish his hot dog, and presumably swallow the coin in the process.
 * The perp buys time to rob his victim's house by asking the victim to add four tubes of toothpaste to his supermarket order of seven items. This required the victim to check out in a regular shopping lane instead of the 10-items-or-less express lane, which otherwise would have allowed him to return in time to see his house being robbed. Brown figures it out because the perp was the last of the victim's friends to ask for items, and his order was too plainly designed to surpass the Express Lane Limit. Of course, the fact that the perp counted on both the victim and grocery staff to obey the letter of the express lane rules and for the express lane line to be open and available at the same time he was at the store pretty much means he deserved to get caught.
 * Bugs Meany holds a raffle drawing at a fair for a baseball glove and has one of his friends reach around for another associate's balls in the big container of ping-pong balls. Encyclopedia discovers he was cheating by noticing that Bugs drank a canned soda when he was carrying around a thermos, thus meaning he put the ball in the freezer, then took it to the fairgrounds in the thermos so the associate would just have to feel around for a frozen ball. It's entirely possible that Bugs simply didn't want whatever was in his thermos at that particular moment or was saving it for later. Or that he'd already emptied his thermos, and found himself wanting another drink.
 * Two precious ivory bookends belonging to a former circus owner are stolen when two of the man's friends are visiting. Encyclopedia and his father find strange handprints in the beach near the circus owner's house, and so suspicion falls on one of the visitors, a crippled acrobat, because the only way he could have walked was on his hands. Encyclopedia, however, insists that the thief is in fact the other visitor, a former bareback rider, because she said her leather gloves were missing, and "no one brings leather gloves to a seaside town in the summer." (Because she couldn't possibly have brought the gloves for a legitimate reason like playing golf, as driving gloves, or even riding a horse. And she certainly couldn't have packed them by accident.)
 * It also depends on which seaside city we're talking about. Forget the flowers in your hair, if you're going to San Francisco in July or August, you'd do well to bring a pair of gloves.
 * A perp who's trying to frame Encyclopedia for claiming ownership of the town clock and charging people to use it to set their watches is "proved" as a liar because he used his left hand to set his own watch, because of the "fact" that when you set your watch with your left hand, you're holding it upside down. (Because it's impossible that a person could simply be more comfortable using their left hand, and compensate for it when setting their watch, or that one could buy left-handed watches specifically to avoid this problem.)
 * A perp is accused of stealing something that belonged to Encyclopedia's client, and riding away on her bicycle. She claims that she hasn't ridden her bike all summer, before she takes it out of storage and starts showing off on it. Encyclopedia declares that she's lying, because if she hadn't ridden the bicycle like she claimed, the tires would have gone flat. (Because it's impossible that the girl or her parents could have kept the tires inflated in case she ever decided she wanted to go for a bike ride.)
 * A man tries to claim insurance money on a painting he's reported stolen. His story goes that while shaving after a shower, he saw reflected in the mirror a man stalking away with the painting. Encyclopedia explains that the claim is a fraud because a mirror would be foggy after a shower and so the man wouldn't have been able to see anything. (Never mind that it only takes a second to wipe away condensation, something people often do when they need to shave. Or cold showers, or how movement and shapes are still discernible through a foggy mirror. Or how some people use a fan or leave the bathroom door open specifically so that the mirror doesn't fog up in the first place!)
 * A sailor wins a painting contest open only to amateurs. He is called out as a professional painter pretending to be a sailor because he failed to do the research on nautical terminology: he used terms like "left" or "right" when describing a boat he was painting rather than the nautical terms like "port" or "starboard", as well as the redundant phrase "knots per hour,", mistakes that no one remotely familiar with sailing would have made regardless of their expertise level. However, while "he's a professional painter trying to pass as an amateur" is the most likely explanation for the masquerade and was probably sufficient grounds on its face to get him disqualified, he might have had other reasons for the pretense and it's not ironclad evidence he's an actual professional.
 * Still another case hinged on the detective's belief that a real resident of San Francisco would never ever refer to the city as "Frisco." While it's true that residents of the city traditionally hate that nickname, it's not exactly an enforced law, at least not since Emperor Norton died.
 * A case had a kid that finished last in a race correctly identify a song being played at a theater along the race route as "The Eyes of Texas," rather than (the presumably more identifiable to a kid in Idaho) "I've Been Working on the Railroad," "proving" that he stopped in to ensure that he would finish last. Because he couldn't simply have been a football fan who had seen the Longhorns play. This compounded by the fact that the two songs aren't even the same - "I've Been Working on the Railroad" has more lines, to a different tune.
 * A blind man is the only witness to a crime; a perp fleeing the scene with a bag of cash crashed into him, and it is thought that the man might have felt his face well enough to identify him if he felt it again. Turns out the blind man is not blind, and was in on it the whole time: he swapped bags with the thief when they collided. How does Encyclopedia prove this? When he visited the man in his hotel room, the lights were on and there was a newspaper on the table despite the man claiming he hadn't had visitors in "a long time". Because no hotel in the world offers complementary newspapers that they put in your room. And they never have the lights on when you arrive. And a blind man would totally notice if they were on, and turn them off. This is a lesser example, however. Once Brown figures out what happened getting a doctor to confirm that the guy can see shouldn't be too hard.
 * Bugs steals an antique teacup. When Encyclopedia confronts him about it, Bugs claims that that it was prized cup from the owner of a Chinese restaurant that has since gone out of business. Encyclopedia deduces that he's lying by noticing that the cup has a handle, which Chinese teacups do not have. (Because it's impossible for a Chinese guy to like American mugs.)
 * One story had a girl having one of her sneakers stolen from her before a sneaker contest was held. The thief was identified because she said to another person that the girl had the sneaker stolen from her "while clipping her toenails", even though all the girl said was that she was "clipping her nails". And only the thief would know that she had been clipping her toenails and not her fingernails (Even though if someone said she had her sneaker stolen while clipping her nails before a contest involving feet, most would immediately assume the nails WERE toenails, not fingernails.)
 * Another story involved Encyclopedia Brown solving a case because a suspect came to the door with tears dripping from the outside corners of her eyes; from this Encyclopedia deduced that she was faking tears, since tears come from the INSIDE corners of your cheek. Where tears really overflow from the eye's surface onto the cheeks depends on the structure of the individual's eyes, how puffy and irritated they are, and the tilt of the weeping person's head, among other things.
 * Encyclopedia's dad described a case to him after the fact that involved a professional tennis instructor who reported that a set of ivory screens had been stolen that morning. He saw the thief's face; it could be either of two identical twins -- one who worked as a cashier and one who played tennis. Encyclopedia figured out that the victim was just lying so he could get insurance money for the screens. The incriminating evidence? The crook was wearing a T-shirt, and if the tennis player had been the culprit, one arm would be more developed, while equal arms would incriminate the cashier. Granted, the "victim" was also a tennis player and was familiar with the twins, but being tied to a chair with a gunman in your house is not the time to expect Holmes-level analysis. More likely, his head held no thoughts but "call 911".
 * The solution itself is faulty as well; Encyclopedia has never seen either twin's forearms to know just how distinct they might be from one another; for all he knows the tennis player's arm might have atrophied from years in retirement, or he keeps them both in shape, or the cashier plays tennis as a hobby and might be developed as well.
 * There's also the possibility that said twins are ambidextrous, which Encyclopedia shouldn't have ruled out either.
 * And it's not even a necessary gaffe, as calluses on the tennis player's racket hand probably would be a valid clue to their profession, unlike forearm musculature, which any sort of exertion can cause to bulk up.
 * In one story, a man claimed an item of his had been stolen during a thunderstorm. The house was dark because the power was out. He was awoken by a thunderclap, then saw the burglar in the lightning flash that followed. E Brown knew that the man was lying (he had actually stolen his own property for the insurance money, then made up the story), since in real life, thunder follows lightning, not the other way around. Of course, it's inconceivable that there would be more than one lightning flash during the course of a thunderstorm.
 * A contest is held in which contestants complete a quiz for 3 secret prizes for 1st, 2nd and 3rd place. The first place winner receives the best prize: a watch, which he discovers has been broken. The theory of the crime is one of the contestants secretly examined the prizes and played with the watch and broke it. The culprit turns out to be the 2nd place girl that purposely missed a question she should have gotten right: "Name a word that has three double-letters." The girl referred to herself as a "bookkeeper". Assuming she remembered such a fact, the solution fails to prove why she threw the contest or definitively eliminate her from the suspect pool of the other contest losers.
 * Isn't there also the possibility that she thought she was saying book keeper rather than bookkeeper?
 * Even assuming she knew the proper spelling of the word she said aloud, knowing a fact and being able to answer a question in a quiz about the fact are two completely different things-- as anybody who's participated in a quiz can testify.
 * One case was solved because the culprit claimed their wobbly table was knocked and various possessions spilled on the floor. EB points out that the table was three-legged, and that such tables can't tilt. Three-legged tables won't be wobbly even if the legs are different lengths. However, if the table was on a slant to begin with, jostling it might very well knock it over, or at least knock the items off.
 * A client's entry in an art show is damaged by one of the three friends he had over at his house. Encyclopedia identifies the culprit as the one who went into the kitchen to look up the meaning of the word "misled" in the dictionary, because in spite of a friend's suggestion that it was the past participle of "misle", he correctly managed to find the meaning in the dictionary entry for the differently-spelled "mislead". Because he never could have seen it elsewhere on the page or ignored his friend's suggestion.
 * At least one time the series used this trope absolutely correctly. Bugs claims to have been kidnapped at Encyclopedia's behest (how a 5th-grader was able to hire and control adult Mooks is never discussed). He describes being imprisoned in a small room, and attempts to escape by removing the pins from the door hinges, but they are on the other side of the door. Then he tries to wait to the side of the door and jump his kidnappers when they come in, but the door opens into his face, foiling the attack. Standard house doors cannot open away from their hinges, only toward them.
 * Encyclopedia Brown liked solutions where the answer hinged on an American city having the same name as a foreign place that was generally more famous, for example Paris, Texas. This isn't usually conviction by contradiction, but became a case of it bordering on Unfortunate Implications in the answer to one puzzle involving an American city called Palestine, where Encyclopedia declared that it had to be the American city because "nobody calls the real one Palestine anymore." Apparently in Encyclopedia Brown's world, Palestinians don't exist.
 * A boy gets injured in the foot by an unknown suspect. Another boy is asked to bring a spare shoe for the injured party. Brown deduces the other boy is the perp because he brought the right shoe for the injured foot without asking beforehand which shoe to bring. While common sense might suggest to the boy to think about which foot would need the shoe, he still had a 1 in 2 chance of getting the right shoe if it didn't occur to him right at that moment to ask and, although the wrong shoe might not fit comfortably, it could still fit his foot if the size allows for enough space.

Comic Books

 * The Swedish edition of The Phantom had a few pages of reader-submitted letters and material for a long time; one mainstay was various whodunnits, of course concocted by one of the readers. While some were well-written, far too many that hinged on the culprit making any kind of factual fallacy (such as stating that Canada's capital is Toronto) which immediately had them busted. The one that set off the trend was admittedly fairly good; someone disguised as a Muslim Imam, who orders a ham sandwich...
 * One whodunnit was a murder taking place in Germany, and one suspect claimed to have been in the woods picking berries at the time, while the other said he had been at the movies seeing a Bond movie, and remarked on Bond's funny German accent. While the readers were supposed to suspect the latter (Bond is German?), certain little-known cultural traits were at work - movies are always dubbed over with German speech in Germany, whereas picking berries in wooded areas you don't own count as theft and/or trespassing, in contrast to Swedish law which allows it. Although one has to wonder why a German person would remark on an accent being German. (If he thought it was a funny kind of German accent, that still wouldn't be the likely way of putting it.)
 * One early Supergirl comic featured a woman impersonating a man claiming to be Supergirl's husband-that-she-forgot-she-had, in order to make her (the woman's) boyfriend give up his crush on Supergirl. Supergirl saw through this at the beginning, because the woman put "his" arms around Supergirl's neck when "he" kissed her rather than around her waist, which is apparently something only girls do. Though she should be able to literally see through the disguise, being Supergirl.
 * The first storyline in which Superman and Batman learned each other's secret identities (via Contrived Coincidence) featured Batman concluding that someone was lying about being an electrical engineer because he wasn't wearing rubber-soled shoes. On a holiday cruise. While a) Superman had X-ray-spotted a gun in the suspect's pocket and b) the guy did claim to have a job to do in a few minutes on the ship's generators, it's still rather jarring that "The World's Greatest Detective" apparently concluded that no-one can own more than one set of shoes.
 * Inverted in an Archie Comics story, of all places. When Betty is framed for academic plagiarism, Archie investigates the evidence against her and points out the flaws in it that prove her innocence. He then offers actual physical evidence that proves that she was framed by a jealous rival.
 * Inverted again in another story where Archie accidentally spills paint remover on an 1870 Frederick Church painting that Mr. Lodge buys from an art dealer. Mr. Lodge is predictably upset, but then Archie wipes away more paint and finds the signature "Picasso". Mr. Lodge is suddenly thrilled, thinking that he's actually discovered a long-lost painting by Pablo Picasso, but then his butler Smithers reminds him that Picasso was born after 1870, the date when Church supposedly painted his picture. When it dawns on Mr. Lodge that Church couldn't have painted over Picasso's original painting if Picasso wasn't even born yet, he realizes that he's being conned. Mr. Lodge then takes back his check from the crooked art dealer, and gets Smithers to help him literally throw the dealer out of the house.
 * Yet another story had Archie and Jughead housesitting for Mr. Lodge and Veronica while they went on a family trip. A crooked art dealer and one of Mr. Lodge's security guards use the opportunity to steal Mr. Lodge's collection of priceless paintings and replace them with forgeries, while trashing the Lodge house to make it look like Archie and Jughead threw a Wild Teen Party and distract Mr. Lodge. When he comes home, Mr. Lodge falls for it and is furious with Archie and Jughead, but then Archie realizes that the paintings weren't at all damaged by the "party". He convinces Mr. Lodge that they were hung after the wrecking was done, and proves that they're fakes. Archie and Jughead then direct the police to the art gallery, where they find Mr. Lodge's real paintings. Archie explains that the crooked art dealer couldn't bear to damage his expert forgeries and ended up tipping Archie off to the fact that they were fakes, which makes this a case of Hoist By His Own Petard.
 * Regularly parodied in Viz magazine's strip Spot the Clue, supposedly written by a different guest celebrity every month.
 * When Tim Westwood "wrote" the strip, the murderer gave himself away by referring to an album that hadn't been released at the time the strip was set.
 * When David Bellamy "wrote" the strip, the murderer revealed himself by giving a plant's botanical name in capital letters in his speech bubble.
 * When Albert Camus "wrote" the strip, the murderer's lie was to say he enjoyed life, when in fact the inevitability of death renders everything we do meaningless and absurd.
 * Trixie Belden had several comic book stories. One involved a female suspect hiding out as a guy. The crook forgot that female shirts tend to button on the opposite side.
 * The Bruce Wayne: Fugitive arc toyed with this; every time one of the bat-family found some piece of evidence indicating Bruce had been framed for Vesper's murder, someone would pipe up with the obvious: Bruce was more than capable of forging/planting that very same evidence to make them think he'd been framed so no amount of forensic evidence would ever clear him in their eyes. Ultimately, they decide to have faith in his innocence based on their personal experiences with him and not solid evidence of it.

Film

 * Played with in Dogma -- Loki argues to Bartleby that a couple is adulterous because "No married man kisses his wife like that." Bartleby retorts that it's a good thing Loki's never had to serve on a jury. So Loki asks the couple. Hilarity Ensues.
 * In Inglourious Basterds, Hicox is doing a good job of staying undercover... until, rather suddenly, the German soldier he's been talking with says that he's given himself away. The audience is not told what the mistake was until much later: He used the British hand gesture for "three" (index, middle, and ring fingers raised) instead of the German one (thumb, index, and middle fingers raised). German audiences naturally pick up on it more easily, aided as well by the fact that the German character visibly reacts to it.
 * In two of the three endings to Clue, Wadsworth deduces that the cook used to work for Mrs. Peacock's, and that Mrs. Peacock had killed her, because Mrs. Peacock said that what the cook had made for dinner was one of her favorite recipes--"and monkey's brains, though popular in Cantonese cuisine, are not often to be found in Washington, D.C."

Literature

 * Some examples from Donald J. Sobol (the Encyclopedia Brown author)'s less famous solve-it-yourself series for adults, Two Minute Mysteries, starring Detective (no first name given) Haledjian:
 * Haledjian knows someone is the culprit because he claims that a cook in the kitchen was yelling and waving a bright red lobster before he was found murdered. The lobster wasn't supposed to be cooked yet, and lobsters are only red when they're cooked. However, that detail wouldn't be impossible, just weird. The back cover of a regular mystery might well say something like, "Why was the cook waving an already-cooked lobster before he was killed?" Another question is, was the cook yelling because the lobster had already been cooked?
 * Haledjian knows that Nick the Nose, the informant, is lying (as he always is), because he claims that a dying Brazilian's last words were in Spanish, and the national language of Brazil is actually Portuguese. (Because the Brazilian couldn't be one of the many immigrants to Brazil from nearby Spanish-speaking countries. And because it would be impossible for a native Brazilian to speak his last words in a foreign language. And because it would be impossible for an Anglophone informant to simply mistake Portuguese for the extremely-similar-sounding and more commonly heard Spanish language.) In fact, depending on what he said, it could sound exactly the same in Spanish or Portuguese, especially from the mouth of a dying man (who presumably isn't speaking particularly clearly).
 * One of the cases involved the apparent suicide of an actor and Haledjian claiming that the note left behind was a fraud written by an English rival of the deceased because the note used "theatre" instead of "theater" and other British spellings. (Because apparently, Americans are only supposed to use American spellings. And no one ever uses "-re" to refer to stage productions and "-er" to refer to a local multiplex.)
 * This one is particularly egregious: most actors, even American ones, probably would spell it "theatre", unless they were specifically referring to a movie house.
 * Another case has Haledjian declaring someone's alibi faulty because the person identified the tune a band was playing as "God Save the Queen" rather than "My Country, 'Tis of Thee" (which has the exact same tune), and so knew about a British performing troupe being in town. Many American Gilbert and Sullivan companies play "God Save the Queen" before performances, and as a Standard Snippet, it's always "God Save the Queen." Even worse, the actual name of the tune is "National Anthem."
 * And again involving another race runner, where "The Theme from the Lone Ranger" is identified as "The William Tell Overture". Apparently Sobol liked this one.
 * The alleged murderer claims to have not visited his friend for days, but is caught because he leapt over the freshly-painted stairs and knocked on the window set into the door rather than the freshly-painted door itself. (Because it's not like fresh paint looks and smells like fresh paint, especially fresh white paint. And because it's not like some people leap over stairs as a matter of course, or like knocking on a window is often simply louder than knocking on a heavy door.) This is one of the many cases that were recycled for Encyclopedia Brown to solve.
 * An English professor's suicide note is considered fraudulent and a product of foul play because it contains a split infinitive. (Because English professors always follow grammatical rules, even when distraught and suicidal, and all English professors accept "don't split infinitives in English" as a rule.)
 * A variation on this has actually happened in real life. An old, very cultured, French widow was found murdered in her villa, with a note on the wall in blood that implicated her gardener. However, it said (in French), "Omar m'a tuer" ("Omar to kill me") instead of the grammatically proper and phonetically identical "Omar m'a tué" ("Omar killed me."). They still haven't solved the case.
 * One also has to wonder why a dying person, writing in their own blood, would bother to write more than 'Omar'. Why not throw in the murder weapon, time of the event, and description of the room while you're at it? "Omar killed Me in the Villa with..."
 * An inversion of that was actually used as a clue in the book Something Wicked by Alan Gratz. The name of the victim's son, Malcolm, is found written in blood next to the body... except everyone, including the victim, called his son Mal, and why bother with the extra four letters if you're dying and the first three are sufficient?
 * A situation that was almost exactly the same cropped up in one of Jim Sukach's Dr. Quicksolve books. The suicide note said "if I were him" instead of "if I were he".
 * Similarly, in an Encyclopedia Brown case, a note about who was supposed to receive some calendars couldn't have been written by a math teacher because it says "divide the calendars by 1/2", which would actually be multiplying by 2, because math teachers never make mistakes in grammar or use common English-language phrasing fallacies outside of the context of the classroom.
 * Haledjian also dealt with the rather more plausible inversion, where the suicide note was in perfect grammatical English despite the dead man being an uneducated Italian immigrant who read the news in an Italian-language newspaper.
 * A similar situation occurs in A Series of Unfortunate Events. Grammar Nazi Aunt Josephine's alleged suicide note contains several grammatical errors, leading the Baudelaire siblings to believe it is a forgery. It turns out that
 * The suspect claims it is his first time in the victim's house, but when a doorbell rings, he knows to answer the back door. (Because nobody can hear where a given sound is coming from, and it's certainly not that front doors often always have a double ring (ding-dong) and back doors a single ring (ding). And because there's no way at all the suspect could be from, live in, or have lived in a town where it's customary to do everything at the back door except on special occasions.)
 * The painting's owner claimed to be getting dressed to investigate the disturbance, with his right leg in his pants and his left leg out. (Everybody always gets dressed and undressed left-leg-first. Didn't you know that?)
 * A criminal's itinerary read "Palestine" instead of "Israel", thus revealing he wasn't actually going to the Middle East as his girlfriend claimed. (Not a lot of tolerance for potential political differences.) Encyclopedia Brown got this one too. His dealt with a list of international locations which turned out to be cities in Texas, and "Palestine" was the clue.
 * Ironically, a better inconsistency that wasn't part of the solution but was instead mentioned earlier by Mrs. Brown was that the list mostly had individual cities (London, Paris, Odessa, etc) but didn't list a specific city in Palestine.
 * Sobol really really liked making the solution hinge on phrasings that can be either of two different sets of words, in both Encyclopedia Brown and 2-Minute Mysteries.
 * "An arrow flight away"/"A narrow flight away": The detective was specifically looking at the flight of stairs when he said it and the suspect still replied "then why don't you go outside and look for it?", rather than "upstairs", revealing that he knew that the stolen diamond had been shot out of the house with a bow and arrow.
 * "Flawless"/"floorless" The police have confiscated a car whose floorboard was used to smuggle drugs. Haledjian is trying to catch the crooks by posing as car salesman "Flawless Phil". He mentions to one prospective buyer that "the interior is floorless"; when the buyer walks away, Haledjian orders him arrested on the grounds that had he been innocent, he would have heard "floorless" as "flawless", the slogan of the lot. While there are accents that make 'flawless' and 'floorless' sound similar or even the same, there are many more where they are quite distinct. And in either case, isn't it possible that the guy just didn't like the car or perhaps he had to take a dump?
 * Two Minute Mysteries also recycled the "Frisco" clue discussed in the Encyclopedia Brown section above.
 * In one of the Two-Minute Mysteries, the suspect was caught after Haledjian said the (diamond?) was hidden in the cupola because the murderer was the only one who ran up towards the attic instead of to the kitchen. Because only a murderer could know that a cupola (usually "KOOP-ul'uh", but the pronunciation varies by person enough that "kupp-ola" wouldn't be suspicious) was a term for the little domed thing on top of the house and not just an annoying term for a cappuccino maker, that only someone who had killed the house's occupant would assume that the stairs going up lead to the roof level, and that it's impossible to see a cupola from outside the house.
 * 'The Case of the Escobi Sapphire'. A man has a heart attack and dies. His secretary claims that a week before his death, he gave her the Escobi Sapphire, a very large and valuable sapphire set in a ring (which was found in her possession) and she kept it hidden because she feared the family would be angry. The dead man's niece claims that he left the ring to her, and when she visited him an hour before his death, he was wearing the ring on his right hand, so when he turned a page the sapphire flashed brilliantly. The issue is now whether the secretary stole it off the body or whether the niece lied. Haledjian figures that the niece is lying because the dead man was reading a book written in Hebrew before he died- and Hebrew is written right to left. The man would have been turning the left page with his left hand, not the right page with his right hand... But most people turn the page with their dominant hand, regardless of direction. If Haledjian had been correct here, then people would use a different hand to flip back through a book than to flip forward through it. Even animators knew this wasn't true.
 * Overall, though, this series tends to deal with it in a better way than Encyclopedia Brown, in that the stories are SO short that Haledjian only has time to declare that he believes the suspect is lying, not necessarily guilty.
 * Sometimes, Haledjian completely disregards sheer stupidity as an answer. In one mystery, he was on his way to a BBQ when the host was found murdered. His neighbor came over, saying he heard his wife scream in horror, and during the interrogation, spotted the wife's pearl earring in the grill and reached his hand in to retrieve it. The detective told him that he obviously planted the earring because, despite having just arrived, he knew that the coals were cool enough to plunge his hand into them. Apart from the fact that coal visibly whitens when heated and that people can sense heat when standing next to hot coals, does he ever consider the fact that the guy could have just been an idiot?
 * In one case, the head of an orchestra had two skilled violinists and had to decide which would play a solo on opening night. He picks A about five minutes before the performance is meant to start. When he goes to get A, he finds A has been killed, and then has to pick B. Haledjian decides that it must have been B who did it, because B walked onto the stage, sat down and began to play, when he should have tuned his violin and rosined his bow first. Like it's totally unthinkable that someone with an equal chance of getting a part would get themselves ready to play it, especially if the choice wasn't going to be made until about five minutes before it was meant to begin.
 * There was one book of "Solve it yourself mysteries" intended for kids which seemed to do something with the trope while inverting it with more common examples. (e.g. saying a nurse was likely sending threatening calls because there were babies screaming in the background, puzzles about time zones ) One case involved "I was woken up by thunder and then saw a man stabbed during the lightning" because lightning always comes before thunder. Yeah, makes sense, but apparently, there was only one strike of lightning.
 * Another case from the book had a murder take place at a country club wherein someone was pushed down a hill and broke his neck in the fall. The tennis player who reported it was apparently the murderer because he had a grass stain on his shoes and of course, tennis players would have different shoes for tennis than walking around in the grass. Yeah, you'd have a point there, since many tennis players keep a separate pair of shoes specifically for Tennis the way people do for a lot of sports, but apparently, the grass stains certainly couldn't have come when he ran over to see if the victim was okay or not. (In real life, it'd have been more suspicious if he stopped to change his shoes like the detective thought he would.)
 * The "Thunder and lightning" is used in one - the witness is apparently the perp because she was woken up by a bit o thunder, and saw her husband get stabbed in the flash of lightning. Now wait a minute - she could have been woken up by a different thunderclap, and saw the man get stabbed right before the next one. It was a thunderstorm.
 * Another one had a victim killed by having a heavy clock dropped on his head, and there were two murderers. All three suspects claim it was most likely an accident. Person #1's alibi was that he was watching a TV show at the time of the murder. Person #2 hears something fall to the floor from down the hall and runs to investivate, and person #3 was out smoking, then walked in and simply found #1 and #2 standing over the body. The detective says that Person #1 and #2 are guilty for several reasons. One, the clock stopped at 8:51 and no TV show ends at 8:51. This is an analog clock (the stories were written in the 70s) and evidently, there's not the possibility that it might have been simply running slowly (or that the clock's hands got jarred by the impact). The second one also apparently couldn't have heard the body from the other side of the hall, but it's actually not impossible to hear something heavy fall to the floor, especially if it's a clock heavy enough to kill someone.
 * Lampshaded in one story where the detective is listening to someone's testimony on a crime, and mentions it won't stand up in court because he was telling the story as he saw it, through the mirror of a car.
 * Isaac Asimov lampshaded this in one of his stories, in which a character points out that in most detective stories all the detective's deductions could easily be picked apart by a competent defense lawyer and it's a good thing the detective is always able to use their deductions to make the perpetrator panic and incriminate themselves before they go to trial. That didn't stop him from flirting with the trope himself, though.
 * In one Isaac Asimov short story, two similar-looking girls work in a library. One of them murders the other, but claims she has an alibi -- she was accepting a book return from a student at a certain point before the murder. The Sherlock determines that she was lying, and in fact the other librarian accepted the book, because the murderer didn't remember the name of someone who returned a book. He shared a name with the author of a book very well known to any librarian in that university. Not much evidence, but since she confesses later, that's what would matter in court.
 * It wasn't just a locally well-known author, but the author of THE chemical reference, period. A professional chemistry librarian could no more forget the name "Beilstein" any more than a conductor could forget an applicant named "Ludwig van Beethoven".
 * Asimov wrote a whole slew of anthologies in the Encyclopedia Brown vein, wherein the members of a men's club would discuss various mysteries during their monthly dinner at their favourite restaurant, until their waiter provided them with a solution. His use was usually more justified, as, not adhering particularly strictly to the Encyclopedia Brown formula, the Black Widowers were usually pursuing a problem purely as an intellectual exercise, and more often than not, their goal was not to find a legally substantial argument, but just to construct any explanation that was entirely plausible and fit all the facts. (For example, one of the "cases" they tackle is to work out the subject matter of Professor Moriarty's doctoral thesis.)
 * One of those stories inverted this trope by having the shaky evidence (that an accountant would associate the phrase "half past eight" with 8:50 since "eight and a half dollars" is $8.50 and accountants are marinated in money) given to a defense lawyer with an innocent client, so that he can use it to impeach an otherwise unshakable witness. The story was written at a time when digital clocks were still relatively new.
 * In the above story, "What Time Is It?", the characters admit that, while not conclusive evidence, this could be used by the guest, a defense attorney, to sow reasonable doubt in the minds of the jurors, allowing his client to be acquitted.
 * Asimov also wrote a Union Club short story called "No Refuge Could Save", in which a man is identified as a German spy because no American could possibly know all four verses of the Star Spangled Banner.
 * Questions like this were actually used to find spies, at least in the movies, but it was usually reversed -- failure to know the National Anthem or last year's World Series champion was considered "evidence" of espionage. Asimov's joke was that spies who knew about that system would overprepare. In addition, Asimov had very strong feelings about the song, and considered it a tragedy that Americans didn't know it. He also wrote an essay about the importance of all four verses.
 * Asimov had a habit of writing mysteries in which the detective is either an amateur or a professional outside of his jurisdiction, so that he has no legal weight behind his investigation. The detective has a Eureka and figures out whodunit, but the only way to convince the real authorities to even arrest the criminal is to resort to Perp Sweating. The novels Murder at the ABA, The Naked Sun, A Whiff of Death (aka The Death Dealers) and The Robots of Dawn all fall into this pattern. Darius Just, the hero of Murder at the ABA, makes a point of saying that his deductions were all founded on circumstantial evidence and a defense attorney would never have let his argument stand.
 * In one of Asimov's short mystery stories, the culprit is a Québécois person using a false identity of an American. The detective tricks him into revealing his true identity by asking him to write the word "Montréal", and he writes it with an accent aigu on the e, whereas someone who only spoke English wouldn't spell it that way.
 * Because it's impossible that the man could have taken French in school and learned the correct way to spell it.
 * In his short story The Singing Bell, the evidence against the culprit would never stand in court, but it is enough to convince the police that he is guilty, and therefore can have his mind read (which, by law, can only happen to an individual once) for further evidence.
 * In another short story, The Dying Night, featuring the same amateur detective, he is able to figure out who the killer is not only through very circumstantial evidence, but one which wouldn't even work today due to Science Marches On. In this story, the victim was killed because he had discovered the secret behind teleportation, and the killer wanted it for himself. When they entered the bedroom of the victim, everyone sees the sun shining through a window. One of the suspects, who had spent the last 10 years living on Mercury, leaps to the window in apparent fright, and spots the exposed film containing the information on teleportation. The detective surmises that he is the killer, since only he would hide exposed film out a window at night, forgetting that the sun would eventually rise. At the time the story was written, it was believed that Mercury always had the same half facing the sun. Asimov admitted the gaping plot hole this created in his story, but since the discovery had been made long after the story was published, he didn't see any point in trying to fix it at that point.
 * A series of short plays for kids published in the UK featured a detective with the Catch Phrase "And I can prove it, because you made four silly mistakes". The mistakes rarely proved anything. (In fact, one of them was the fallacy namer for No True Scotsman; a character during the Jacobite Rebellion is exposed as an English spy because, amongst other things, he puts sugar on his porridge...)
 * One short story in the anthology Alfred Hitchcock's Sinister Spies is called "QL696.C9", by Anthony Boucher. It's about a librarian who was killed, leaving a the titular mysterious sequence of letters and numbers nearby. At the end of the story, the detective gathers the suspects in the, um, library in the traditional fashion, He's interrupted by the need to keep the murderer (a spy), from killing herself with the pistol she hid in her blouse. Turns out he knew it was her as soon as he figured out what the code was for, as the killer had the only name that was a noun, and the whole library scene was just to flush her out. Fridge Brilliance kicks in when you realize that the detective needed something from the suspect to avert this trope, since there's all sorts of perfectly good reasons a librarian would have to write down a Library of Congress reference code . Ironically, the anthology in question comes up when you search the LoC for the code.
 * Woody Allen, in one of his books, wrote a parody of the detective-catching-one-mistake trope (Match Wits with Inspector Ford). The situations and answers were all absurd. For instance, a kidnapping victim returns home by asking his kidnappers if he could go to a football game that he only had one ticket for. The detective figures out that he's in on it with the kidnappers, because his parents are in their 80s and he's 60 years old, and "nobody would kidnap a 60-year-old man, as it makes no sense."
 * John Dickson Carr specifically warns aspiring mystery writers about this kind of clue in his essay "The Greatest Game in the World." Of course, if you do what he advocates, having guilt depend on a series of clues rather than just one, you won't have that problem.
 * Uncle John's Bathroom Reader had a series of simple mysteries featuring Leslie Boies and her companion, Steve. In one story, Steve tells Leslie about a man whose life was saved because the night watchman at the factory he owned told him he dreamt the train he usually took was going to crash. So the man waited for a later train, and sure enough, his usual train crashed. Leslie comments that the watchman should be fired, because if he dreamt about the train, he must have been sleeping on the job. Because he couldn't have had the dream when he was back at home, clearly. This is a variant on the tale that actually introduces the element that makes this Conviction By Contradiction; in other versions, the dreamer specifically states that he had the dream at a time when he was at work.
 * In one of the stories in Maurice Leblanc's Arsène Lupin book The Eight Strokes of the Clock, Lupin determines that one of the extras in a silent film is infatuated with the leading lady solely from the out-of-character lustful gazes he casts upon her in the film. (These days, we'd just call that "bad acting".)
 * In one of the original Miss Marple "Tuesday Night Club" stories, Miss Marple bases her conclusion on the fact that the gardener wasn't really a gardener, because he was working on Whit Monday. Justified Trope, because she's not trying to convict him, just solve the crime as a puzzle.

Live Action TV

 * Occasionally Cracker falls victim to this trope, with profiler Fitz often using "Encyclopedia Brownisms" rather than genuine psychological insights. In one episode, he deduces that someone is the murderer, as they claimed to be a student and "you don't dress like a student" (because obviously, all students dress exactly the same way). In another episode, he not only deduces that someone is a closet gay, but also his alibis, because when questioned he said "I was at home with my girlfriend" rather than "I was at home with Lesley" -- thus showing he was afraid of saying that his girlfriend's name was a potential man's name and letting Fitz think he was at home with a man (because, of course, everybody normally says "I was at home with [name]" to complete strangers, despite the stranger not having a clue who [name] would be).
 * In cases like these, it's hard to tell if Fitz actually deduces from these facts, or if he's got a hunch and is using some detail to prod (or, rather, bulldoze) a suspect's nerves. There are instances where his 'gotchas' are shown to be ineffective, immaterial or just plain wrong, and he merely forges on until he gets a hit. There is no denying his huge deductive leaps from small details, however.
 * Played for laughs in an episode of Black Adder Goes Forth: Blackadder reveals he discovered Nurse Fletcher Brown was a German spy when he questioned her about her well-educated boyfriend "Who went to one of our great Universities -- Oxford, Cambridge, Hull. You failed to notice that one of these is not a great British university." To which General Melchett, a Cambridge man, replies, "Quite right. Oxford is a complete dump."
 * This was actually a playful poke between the actors; Stephen Fry (Melchett) is a Cambridge alumnus, while Rowan Atkinson (Blackadder) graduated from Oxford.
 * Not to mention, of course, that Hull University didn't even exist until 9 years after the end of WWI.
 * And, of course, it was eventually revealed the nurse was innocent (at least of passing on the information that made General Melchett suspicious in the first place), and the episode ends with Captain Darling scrambling to reveal it (just to make Blackadder look bad) as Blackadder tries to stop him.
 * She doesn't deny it at all, and pretty much confesses without actually saying she did it, giving all the traditional 'I thought you loved me' nonsense. So apparently she was also a German Spy?
 * In early episodes of Star Trek: Deep Space 9, Dr. Bashir often mentioned the one mistake he made on his final Academy exam: he mistook a preganglionic fiber for a postganglionic nerve. This was all that kept him from graduating valedictorian. But in the episode "Distant Voices", an alien Hannibal Lecturer in Julian's brain points out what viewers with medical training (including writer Rob Wolfe's wife) caught right away -- a preganglionic fiber and a postganglionic nerve are nothing alike. The alien accuses Julian of getting it wrong on purpose, which later proves to be true, though for a different reason. If Encyclopedia Brown had been security chief of Deep Space Nine, we might have learned about Bashir's Big Secret (he's ) four seasons sooner...
 * Also, there was an episode of Star Trek the Next Generation where hearings were being held of Starfleet officers out of fear that there was a Romulan spy on board the Enterprise. One officer questioned was revealed to have falsified some personal information claiming he had a Vulcan grandfather, when the grandfather was actually Romulan. Everyone, particularly the witch-hunter who started the hearings, took that alone as just-about-proof that he was the spy they were searching for, but Picard recognized that it hardly counted and worked to get the hearings stopped.
 * In Star Trek New Frontier, even in a post-Dominion War world, being identified as having Romulan blood made you incredibly suspicious in Starfleet's eyes (enough so that, when a Vulcan's Romulan blood is found out, she quits rather than take a job where more eyes could be upon her...and turns to the Romulans in desperation, becoming a commander in the Star Empire's fleet), meaning a Starfleet officer with Romulan heritage had a damned good reason for keeping that knowledge secret.
 * Truth in Television. The US and British governments used to not allow homosexuals to work in government jobs with access to sensitive information, ostensibly because they were vulnerable to blackmail by foreign governments. Problem was, the only reason they were any more vulnerable was because their employers had a policy of firing them if they were outed.
 * There was another Star Trek example. One of the books had a Romulan spy hidden among the crew, and the "clue" that lead to his unveiling was that fact that "he separated his food into separate piles, so they did not touch, and ate them one pile at a time." It was explained that this was how Romulan children are trained. Of course, no other race in the universe could have that tradition-or that a person could just not like having their food mix on their plate.
 * Well, he's either a Romulan spy or a normal human eight-year-old...
 * In the first regular Columbo episode "Murder By the Book", the murderer, half of a mystery writing team, sneers that Columbo doesn't have anything concrete on him -- just a motive, the fact that he took out a life insurance policy on the victim, the fact that someone else was murdered shortly afterward who he claimed not to know but in whose house was found a book with a personal autograph in it, and such odd behaviour as opening his mail shortly after finding a body on his lawn, and taking a large sum of money out of his bank account and putting it back the next day. And he's right, these things are all circumstantial evidence. Then Columbo points out that he found a vague story outline in the victim's office; apparently Columbo's (accurate) reconstruction of the murder matches one of the thousands of rough story ideas the victim had been scribbling down over the past couple of decades. The murderer immediately gives in, despite this being easily the weakest piece of evidence presented thus far.
 * Columbo's suspicions are often piqued by this sort of clue, and he always opens his investigation by giving his suspect an opportunity to provide a perfectly reasonable explanation for it. Several "Just one more thing"s later he's backed his suspect into a corner that he can't wiggle out of.
 * The worst part of the episode, though, is that Columbo finds the minor flaws in the alibi but misses what should have been a fatal flaw in the killer's plan -- the police identify that the killer's phone placed a call to the victim's wife, but they fail to look at the time of the call and realize that it was the phone call where she heard her husband get shot, and not the call that the killer had placed to her house (from another phone) ten minutes or more before the murder.
 * Murder She Wrote usually avoids this trope. One of Jessica's most common lines after a Eureka Moment is "I think I know who the killer is. The only problem is, how to prove it...?"
 * Not so much in Season 5. (Coincidentally or not, these are the first eps after the 1988 writers' strike.) They had several eps where the guilty party knew something that anyone might have guessed. Case in point: In "Smooth Operators", the murderer knew that a bum was using a newspaper as a blanket.
 * Many episodes of Monk have Monk using this kind of evidence to determine the murderer from the start. The rest of the show is trying to get proper evidence, as well as motive and method.
 * For example, in one episode, a sports agent has made it look like he shot and killed a burglar who apparently broke into his house and killed his wife (the trick is that he shot the "burglar" with a handgun and the wife with a revolver, then planted the revolver on the "burglar"). Monk suspects the man is lying because he gave the alleged invader one single shot, instead of unloading his gun on him in a fit of rage and fear like someone would do in a situation like that. Further evidence is that the "burglar" had a .22 caliber, the revolver found on the body was a .38 caliber, and there is no .38 caliber ammunition in his apartment.
 * At least in that instance, the suspect did indeed kill the guy and challenging his version of events would indicate murder. In one episode, Monk zeroed in on a teacher for no other reason than he found evidence he hid his wedding ring in his wallet--which meant he was having an affair and lying about it, making him suspect number one in the death of another teacher whom the police assumed (and Monk couldn't prove otherwise) committed suicide.


 * Psych: This is entirely how Shawn Spencer works. He figures out who did, and in some cases, how, then has to prove the why.
 * Of course, the whole point of the show is that he actually claims to have received the information from his psychic powers. Instead of "This spot on your shoe proves you did it", it's more a case of "I can sense that you did it, oh and here's a spot on your shoe that backs me up." Whether this makes a difference to the juries in this show's universe is unknown.
 * The fact that he has to point out the actual clues in order to get the cops to believe him in the first place indicates that yes, the evidence is what matters. Shawn's visions are pretty obviously not part of the legal proceedings, they're just the mechanism by which the cops find the hard evidence they need to prosecute.
 * It was mentioned in an episode that they have something like an 85% conviction rate for cases they're involved in.
 * Shows up quite a lot in Jonathan Creek (which was originally conceived as a British Columbo, after all). For example, from the fact that a piece of film supposedly secretly filmed by a stalker from over a tall fence used a pan instead of moving sideways, he deduced that it was taken by a short man standing on a box, and as the subject's manager was a short man, therefore it must have been him.
 * They sometimes try to justify this by having him say something like "I don't know, it could be just a coincidence, but..." and wait for this to intimidate the accused to blurt out more definitive proof.
 * In an episode of Stargate SG-1, the team is accidentally sent back in time to 1969, materializing in a nuclear silo. The first soldiers to arrive ask, in Russian, if they are spies. Daniel, without thinking, replies with "Nyet," which is enough to convince the soldiers, rather reasonably, that the four unidentified people who mysteriously showed up in a secret installation with foreign looking weapons and understand Russian are, in fact, Soviet Spies.
 * In the Twilight Zone episode The Grave, this happens. A hired gun is asked to go to a grave of his foe and plant a knife on it in a dare. He does so, but winds up dead. The next morning the townspeople go up to the grave, see the man lying on top of the grave. The sheriff deduces that the man completed the dare, but stuck the knife through his coattail, and when he turned to leave, the shock of being restrained so suddenly killed him before he realized what was holding him down. The sister of the man in the grave points out that the hired gun's coat is pinned down in front of him, and standing where he was standing the previous night, with the same wind, it is clear that her shawl is blowing behind her, supposedly proof that her brother reached up from the grave to kill the hired gun. Bugs Meany and Encyclopedia Brown get in on this one: 1) It's not like a man wouldn't ever pull his coat around himself, especially while kneeling. 2) If her argument was that the wind would blow the man's coat too far behind him for him to stab his knife through it, then it most certainly would have blown said coat too far back for anyone reaching out of a grave to get it. If the man wearing said coat couldn't reach it because it was too far back, it would make sense that no one in front of him could reach it either.
 * In the Nickelodeon series The Mystery Files of Shelby Woo, the teen detective identifies the writer of a smudged note - thereby exposing the episode's culprit - as left-handed, because "only a lefty smears when he writes." Which is patently not true. Some righties smear, many lefties don't.
 * Shelby once identified a kidnapping suspect by breaking his alibi; he'd claimed he was at the movies around 8 or so but his ticket stub was for a 5:15. The suspect got irritated that she was going through his things and it was pointed out the evidence was not sufficient to point to his guilt--then he's identified based on his strange habit of drumming his fingers on his briefcase, making the same drumming sound as heard over the kidnapper's ransom call.
 * Another ep had Shelby try to identify a suspect in a smuggling case by the sound of his whistling a particular tune. She told Da Chief it had to be the musician who performed a concert in town whose song the suspect was whistling; Da Chief points out that a lot of people attended that concert and would have found the song catchy, a guy whistling that same tune walks past them and Da Chief smugly points and goes "See"?.
 * In Seven Days, there is an episode where some woman threatens (over the phone) to cause catastrophes unless Frank does as she says. Each time he performs a task, she answers a question. One of the question was about who won a certain year's sports championship. She answers - and that's what proves that she is actually a man. Possibly averted by the fact the person seems to know Frank, and he claims to know no women who could answer this kind of question.
 * On CSI, Brass once fingered the criminal based on the guy saying: "I loved my wife". Apparently only killers talk about the dead in the past tense.
 * To explain further, it's the old chestnut that innocent people whose loved ones just died haven't processed that they're dead, and refer to them in the present tense for a while. Anyway, this is a minor example, seeing as how this wasn't even the specific incident that aroused Brass' suspicions, and he (as you'd expect in a CSI series) still has to get the lab to find him proof before he can do anything substantial. And the criminal STILL wasn't arrested by the end of the episode (though the raised suspicions were enough for the wife's life insurance company to repossess the husband's newly-bought Ferrari).
 * Actually used as evidence in a Pennsylvania murder case--Upon being told two children were missing, the suspect asked "How old were the children?" He died in prison.
 * Of course, the suspect could just be cynical and, like many people, believe that if someone's missing, they're likely dead.
 * In another CSI episode, while searching the house where the female victim of the week lived alone, Sara dramatically announces "the toilet seat is up - a man was here!"... without even entering the bathroom to check if maybe the victim had been vomiting in the toilet (they'd just found a lot of spoiled food in the fridge, after all), or whether she'd been interrupted in the middle of cleaning the bathroom, etc.
 * Criminal Minds: Almost every profile, leading to several false arrests following generic descriptions. This is why profiles are not admissible in court for many jurisdictions. Most episodes end with perp sweating for confessions or real evidence to get around this. The truly strange thing is that even though they are fully aware their generic descriptions are often very wrong to start with, they get extremely annoyed should someone cast doubt when they make a prediction.
 * Occasionally played with in the show, such as in "Doubt". The guy they arrest is obviously the killer, but he doesn't confess and they have no real evidence against him besides the profile, so they're forced to let him go (the fact that a murder with an MO similar to his is committed while he's in custody helped).
 * The team will often catch the perpetrator in the act of attacking their latest victim, thus enabling the real evidence to fall into their lap. The catch is that some episodes will point out how they don't have enough evidence for a warrant and need a pretext to bust into the suspect's property but in most cases, the mere identification of the most likely perpetrator cuts to a scene in which SWAT is breaking down their door.
 * Another ep had the profile as the primary evidence against an amnesiac suspect since they caught him at his home and not in the middle of trying to kill his latest victim as per the usual formula. Lucky for them the suspect regained his memory and led them to another one of his undiscovered victims.
 * Law & Order: Criminal Intent: Detective Goren's entire Modus Operandi is coming up with contradictions to the suspect's story and using them to get the suspect to confess, often with their lawyer fully present. Like it's predecessors, the suspect often gets so upset they decide to confess over their lawyer's objections.
 * There's also the episode where a suspect, a substitute teacher, says he hasn't been to Egypt and learned about the new Library of Alexandria from a magazine article. When the suspect says that the library has state-of-the-art smoke detectors and Goren didn't see that detail in the magazine article, that the guy was lying becomes a major plot point. An arguably more likely explanation, that the substitute teacher was making a lame joke about the fact that the old Library of Alexandria burned down, isn't even considered.
 * On Law and Order, when the police use contradictions in a suspect's story to solve the case for real, they're smart enough to use the it to gather more evidence to confirm the suspect's guilt.
 * One exception was in "Savior": a teenager claims she tried to lift some family jewelry for her boyfriend but when the jewels were missing, he shot her and her mother in a rage. The DA points out she could have stolen the jewelry herself without inviting her boyfriend into the house and concludes instead that she was paying the boyfriend the jewelry to murder her mother and he shot her when the jewelry was missing.
 * ADA Claire Kincaid once suspected a wife of the murder the husband had just been found guilty of. Her reasoning was that in a pretrial interview, the wife tried to cover for her husband's bank account withdrawals (which the victim was blackmailing him for) with a sloppily-crafted alibi. On the witness stand during cross-examination, she stuck to the same obvious lie with no elaboration; having known ahead of time the DA would ask about the money, she had more than enough time to come up with a more plausible explanation.
 * In another episode, a husband's conviction for the murder of his wife hinged on the theory he stole a brooch from her body the police later found with his mother. The defense brings in identical brooches to challenge the DA to prove the one they have is the right one. The victim's lover identifies the brooch from an engraving she'd made on the back of it.
 * In one episode, Cerreta and Logan interview a murder victim's family, and the son tells them that his mother wouldn't have killed his father, saying that he was with her at the time of the murder. Later in the episode, Cerreta wonders why the son didn't say she didn't kill his father, if they were together. Although the variation, while still a leap on the part of the detectives, is rather significant in that if someone is physically with you at the time of a murder, you know full well they couldn't have done it and thus have little reason to prevaricate.
 * Assuming, of course, that all the statements are logically interconnected, and the son didn't actually mean "She wouldn't kill him, and she was with me, anyway, so it's moot." Traumatized families of murder victims aren't always speaking in the most logical thought progression, and it seems odd to take their minor verbal flubs as greatly significant.
 * A variation of the old "I'm innocent" vs. "You can't prove that" giveaway is used in an episode of The Mentalist when the main character sits down three suspects and declares that he's going to have them fingerprinted to see who accessed a certain company computer. Two of the suspects become visibly upset and protest that of course their fingerprints will be on it because it's a public terminal. The third suspect says, "Go ahead. It'll just prove that I'm innocent," which of course immediately arouses suspicion because only the culprit could know that their fingerprints won't be found.
 * Wasn't that on Lie to Me?
 * Crownies features this when a teacher accused of having sex with a student claims that a note the student had in her possession was written to his wife years earlier. Conveniently, the note happens to mention a brand of alcopop that didn't exist at the time.
 * 24 in the first season, Jack is interrogating a businessman in his limo, trying to prove he isn't who he says he is while connecting him with the conspirators in the day's events. His initial "contradictions" are fairly shaky, such as why is an honest businessman is meeting someone in a garage unless the person was a criminal. The real clincher that he's a phony is when he tries to attack Jack with a knife he keeps in a secret compartment of the limo; why would an ordinary businessman who can presumably afford security carry a blade in his car unless the guy he was meeting with was a criminal? Perhaps the guy's just Crazy Prepared? In this case, it may have been as much about the knife itself as the fact that it was a specialized blade: a Microtech HALO that's something only a Knife Nut would procure.

Newspaper Comics

 * Slylock Fox uses this trope in nearly every strip as Slylock's main way of crime solving.
 * Parodied in this Pearls Before Swine comic.
 * Subverted on Calvin and Hobbes when Susie is hit with a flurry of snowballs. She goes after Calvin, who has a wheelbarrow with him, and who protests that Susie only has "circumstantial evidence." She clobbers him anyway, and while lying face down in the snow Calvin claims that "you can't get a fair trial in this town."

Radio

 * One episode of The Whistler featured a man who killed his wife and made it look like a suicide. The police investigation and interrogation, conducted in the wife's apartment, has some close calls, but it looks like he's gotten away with it. The detective rises and heads for the door, ready to close the book on the case...and the wife's alarm clock goes off. Why would someone who's planning to commit suicide set their alarm clock to wake them up? The detective comes back, and says it's time to restart the interrogation from the top, as the husband breaks down.

Riddles

 * A popular (well, often seen) riddle for kids goes like this: The detective is in a hotel room because the hotel's director told him that a famous thief is in the hotel. Then, someone knocks at the door of the detective's room. He opens, and there's a guy, who apologizes: "Sorry, I thought this was my room." The detective arrests him immediately, and guess what, it's really the Gentleman Thief he was looking for. Oh, the reason? Because nobody will knock on the door of his own room - so the thief must've been checking whether the room was empty and he could plunder it! (Because it couldn't be, let's say, that his wife was in the room, had been taking a shower and he wanted to warn her, in case she wasn't dressed yet, and other people were in the corridor. Guess the thief is at least guilty of not inventing a good excuse.)
 * Or he left keys in room while his wife stayed so he had to knock the doors...
 * Another riddle involves the murder of a wealthy man who is killed on a Sunday. Upon being questioned, all of the servants give various alibis: "I was polishing the silver," "I was mowing the grass," etc. The "killer" is the one who claims to have been checking the mail, because mail isn't delivered on Sundays--because apparently, it's impossible to forget that and just check every day out of habit. Or to have forgotten to check on Saturday, and instead get the mail the next day.
 * Or to receive a newspaper that is delivered on Sunday, or any mail delivered by others than the Postal Service (how uncommon this is may vary between countries)

Theatre

 * In The Crucible by Arthur Miller, Sarah Osbourne is suspected of witchcraft because she muttered something after being refused alms when begging. She claims she was just reciting the Commandments, but she cannot recite them for the court and is thus convicted. This is in keeping with the overall point of the work, which is that the trials are inherently unfair and the 'evidence' is flimsy and being twisted by hysteria and malice.

Video Games

 * The first Knights of the Old Republic had a sidequest on Dantooine in which you determine which of two suspects is the murderer by poking holes in their testimonies. During the first round of questions, you find out that one of the two suspects lied, but he's not the murderer and it wouldn't do him justice to accuse him just based on this evidence -- the truth is more complicated and can only be found out by repeatedly questioning both suspects and the forensic droid.
 * You can also bypass the whole "logic" aspect and say that you know who did it and that your reasoning is that "fat people always lie."
 * Mass Effect 2 has a sidequest where Shepard must use various fragments of messages to identify which of five possibilities is the Shadow Broker's chief agent on Ilium. The solution comes down to the use of a single contradictory pronoun to give the answer . Of course you are working for Liara, not the courts, and she's no longer too hung up on the whole 'reasonable doubt' thing.
 * Of course assuming Shepard is correct, even that's not really proof that
 * Although, leaving that uncertainty in tact and making Liara overreact like that is almost certainly intentional, seeing as how it drives home that Liara is acting a few krogan testicles short of a quad nowadays.
 * Nyxeris sure isn't putting much effort into seeming sincere, either.
 * The DOS edutainment game, Eagle Eye Mysteries falls victim to this at least once. Although the guilty party usually tells a very blatant lie that makes everything they say untrustworthy, you usually find other physical evidence too. Not so in one case, where a suspected Moon rock theft hinges almost entirely on the thief calling said object a sedimentary rock, despite the player researching in-game that it is physically impossible for a Moon rock to be sedimentary. No other evidence is found to implicate the suspect. (Because if you don't know your basic geology terms, you are clearly a thief.)
 * Played with in the Ace Attorney series. This trope is literally the core mechanic of the games; your entire job is to find contradictions in witness testimony, either by presenting contradictory evidence or showing that the scene was arranged in such a way as to make their actions impossible. Generally inverted by Phoenix Wright and Apollo Justice (proving a defendant innocent by poking holes in the evidence against them), but played straight by Miles Edgeworth. Naturally, though, the games would be boring if there were no twists; therefore, the trope is averted, subverted, doubly subverted, zig-zagged, and generally tied in knots by pratically every case.
 * One notable moment is when Phoenix proves the witness could not have been the passenger in a car because.
 * The above example isn't strictly conviction based solely on the contradiction; the contradiction is alleged to be proof that the witness was lying about having been a passenger, which is then used to bring out the real secret that the witness was trying to hide with that lie.
 * That said, it's often subverted. Just because there's a contradiction in a witness's testimony doesn't necessarily mean the witness is lying, or even mistaken. In fact, it's even inverted a few times; a seeming contradiction in the testimony sometimes results in a reevaluation of the evidence, changing the tone of the case entirely.
 * Contradictions that exist because a witness in Ace Attorney is lying don't always mean that the witness is the culprit - they could be an accessory to the crime or have a grudge against the defendant, for example. If the witness is the culprit, it will take a minimum of three contradictions to convince the judge that the witness is a murderer (and that's if one of the contradictions proves that the person handled the murder weapon, had a motive to kill the victim, or lied by claiming they weren't there).
 * Presenting evidence to point out contradictions is often followed by the player character answering a question (whether choosing a dialogue option or presenting more evidence), to indicate what the contradiction means. Most of the final presentations to take down the murderer are one of these, rather than a final cross-examination.
 * Completely subverted in one case where you are required to perform several such arguments; your goal isn't to convict the witness, but to prove his memory is unreliable.
 * Thus the Series is a Justified Trope. It actually acknowledges that this rule is faulty and subverts it many MANY times.
 * In the 1st Degree plays with this trope. While the prosecutor is required to poke holes in Tobin's testimony in order to get first-degree murder, it could be argued that Granger achieved it because Tobin had a total meltdown right there in the courtroom and revealed to much information.

Other

 * The Perplex City card "Alibi" pegs as a murderer because she said she was getting the mail at the time of the crime - a Sunday. (Of course, no one ever picks up Saturday's mail on Sunday.)
 * Parodied in an article from The Onion about the boy detective's murder. Bugs claims that "at the time the crime was committed, I was at the North Pole watching the penguins".

Western Animation

 * Parodied in Moral Orel, in which Orel starts a detective agency. There are two suspects when the contents of Reverend Putty's collection basket is stolen: Joe the Devil in Plain Sight, and a clearly-innocent Susie. Orel ignores the expensive ice cream Joe has bought, and the fact Susie wasn't even in church at the time, and bases his conclusions on which Commandments they broke (or didn't break): Joe honored the Commandment about keeping the Sabbath Holy by refusing to cut his grandfather's lawn, while Susie broke the Commandment of honoring her parents by volunteering at a retirement center instead of going to church like she was told. If she broke one Commandment, then surely she would be the sort of person to break "Thou shalt not steal".
 * Double Subverted by Beavis and Butthead, of all people. When our heroes are accused of egging Tom Anderson's house, Butt-Head is inspired by a court reporter he saw on TV to try and discredit Anderson's testimony by pointing out that Anderson couldn't clearly identify who threw the rotten eggs at his house. The judge is about to dismiss the case when the prosecutor objects, stating that neither Anderson nor any of the police reports or court documents had ever said the eggs were rotten. He then asks how Butt-Head could have known the eggs were rotten unless he and Beavis were the ones that threw them. Butt-Head has no response, and he and Beavis are sentenced to 500 hours community service.
 * Rugrats had an episode like this. Angelica has Tommy hold a trial to find out who broke his favorite lamp, with Angelica as a persecutor. She attempts to finger Phil, Lil and Chuckie as the "poopatrator", but all of them have solid alibis. It isn't until Tommy realizes something random  that makes the babies realize that it would have been impossible for her to know what exactly they were doing and thinking unless she was there, which she was.
 * In the first Sideshow Bob episode of The Simpsons, Bart and Lisa's investigation basically comes down to this. First Lisa realises that Krusty wouldn't have used the Kwik-E-Mart microwave because he has a pacemaker, then that he couldn't have been reading the Springfield Review of Books at the magazine rack because he can't read. Sideshow Bob argued Krusty wasn't one to follow medical warnings and didn't need to be able to read to enjoy the Springfield Review of Books. Finally, in a Eureka Moment, Bart remembers that Homer stepped on the ends of fake Krusty's long shoes, which his feet would not have been long enough to fit, but Sideshow Bob's are.

Real Life

 * This is one of the reasons you're never supposed to talk to police officers unless there's a lawyer present. It's quite easy to say something that could be misconstrued as suspicious or incriminating, and police in Real Life are more diligent than in fiction about using holes in a person's statement as a starting point to single out the suspect(s) who will be investigated more thoroughly via obtaining warrants and gather the real evidence that's used in a conviction. When the police tell you anything you say "can and will" be used against you they aren't kidding. Conventional legal wisdom is to invoke your right to an attorney and never speak to police officers if you think the police suspect you of a crime. The lawyer is there as a witness.
 * Police are also more experienced and versed at some of the less well-known cues for discerning between how an innocent person vs. a guilty one will react to being accused of a misdeed and what would constitute suspicious behavior/language:
 * An innocent person accused will deny it, while a guilty person might make a statement that doesn't depend on actual innocence, such as "You can't prove that!". As pointing out that the accusation is by contradiction rather than evidence is closer to the second reaction than the first, it's not unreasonable for Lampshading this trope to trigger a (further) investigation.
 * Another thing is that if someone is telling the truth they will defend it constantly and they will sound shocked and confused, but if they are lying they will sound angry or embarrassed (i.e. defensive) because they've been found out. A guilty person will make up stories as to what they were doing at the time of the incident, often contradicting themselves. They will usually end up confessing due to their feelings of guilt.
 * Also, the "found out as a foreign spy because--" examples are very much Truth in Television if for no other reason than if you're found out as a spy, you're less likely to end up in front of a jury in a public court with all those pesky "standards of proof" and more likely to end up in a dark hole in a location known to no one with the government of the host country giving you some harsh interrogation, and pointing out the holes in their evidence is most certainly going to fall on deaf ears.
 * Though obviously easy to take too far, espionage is at least as much a national-defense issue as a criminal issue, and the primary purpose of interrogating spies is not getting a conviction, it's finding out A) what they've found out and B) how many other spies are in your country, and if possible, who they are.