Perfect Poison

"Shackleforth: "Glove cleaner", huh? Say... you sell much of that stuff? Daemon: Now and again. Shackleforth: By the way, what's in it? Daemon: No trace, no odor, no taste, no way to detect its presence. And it's sure. One thousand dollars..."

- The Twilight Zone, "The Chaser"

When murder by poison is depicted in fiction, it never takes more than a drop of clear liquid or a pinch of white powder in order to make the victim grip their throat, cough a bit, and fall over. Quick, clean, and quiet. The reality is not so simple. Poisoning someone to death in a way to avoid suspicion and police detection is a very complex process.

Outside of highly controlled chemical munitions, there are very few substances available to the average murderer that can kill a human being as easily as the poisons of fiction. Famous poisons like arsenic, strychnine, cyanide, etc. require small, repeated doses to build up enough concentrations to kill without arousing the suspicion of the victim... in significant quantity, such poisons taste extremely bitter (hence the need for medieval food tasters). The mechanisms by which these poisons kill can cause dramatic physical reactions in the victim. And these old standby poisons are easily and routinely detected by modern forensic pathology.

The sort of poisons that can kill very rapidly at small doses tend to be staggeringly dangerous to the poisoner, not to mention exceptionally hard to come by and hazardous to manufacture.

This is generally assumed to be the kind of poison used in a case of Finger-Licking Poison. Frequently has an Improbable Antidote. May or may not be purple or green. Naturally, part of its perfectness is usually that it works on everything.

Anime and Manga

 * Averted in JoJo's Bizarre Adventure, where both victims Dio poisons happen in steady doses over a long time.
 * Subverted in Detective Conan. APTX-4869 is supposed to be one, but certainly for our heroes it's merely a Fountain of Youth.
 * But they do have quite a few incidents where a person is killed by poison from a single dose administered a short time before the victim dies. You'd think the killers would want their target to drop dead somewhere other than the place they were poisoned, to throw the police off the trail and give them time to dispose of the evidence, but that never occurs to them.
 * Partially averted in Naruto: the Sasori's Poisoned Weapons are said to take three days to kill their victim, though they still take an improbably small amount to do so. At least he has a reason not to be concerned about their being dangerous to him (since he doesn't have a real body, and is thus immune to the effects).
 * If it were actually a bio-weapon of some sort, it would explain why it can kill even in small doses, never kills faster, and why it is so difficult to cure. Probably targeting the nervous system, given its paralyzing effects.
 * Another option is Ricin, which usually kills in about 3–5 days. It works by preventing the victim's body from making more protein.
 * Averted in Shina Dark. Poisoning Christina was done over many years.

Fan Works

 * In MGLN Crisis, the poison kills her within a few minutes, before help arrives.

Film

 * Iocaine powder from The Princess Bride is odourless, tasteless, and causes nearly instant death. Apparently there are no ill effects up to death. Yet it's still possible to gain an immunity to it...
 * As Pirate Robert points out, that depends on the dosage. It's actually a noted method that one can develop immunity to certain poisons by consuming harmlessly small doses over time, and gradually increasing the amount for greater tolerance. However, ingesting amounts greater than one's current tolerance will still kill. We also never see how big of a dose he puts in the drinks. (Beware of trying this with other poisons, such as lead—these will simply accumulate in the body until a fatal concentration is reached.)
 * Aversion of this trope is a major plot point in the second half of Alfred Hitchcock's Notorious.
 * The Maids: A cup of tea mixed with an overdose of sleeping pills will cause the victim to peacefully go to sleep in some ten seconds. (In Real Life, it would probably make the person nauseated enough to vomit the pills back up).
 * In Traffic, the police informant played by Miguel Ferrer dies a few minutes after eating one bite of a poisoned breakfast. The only warning was his comment that the food "tastes like shit."
 * In Batman, the Joker's Smilex poison (a variation of his Venom from the comics) is a multi-part poison designed to hinder the police, who assume he's poisoned only a single product. As Batman explains, "Each product only contains one component. The poison only works when they're mixed. Hairspray won't do it alone, but hairspray combined with perfume and lipstick will be toxic and untraceable."

Literature
"Laertes: "I bought an unction of a mountebank, so mortal that, but dip a knife in it, where it draws blood no cataplasm so rare, collected from all samples that have virtue under the moon, can save the thing from death that is but scratched withal." Act IV, Scene VII."
 * Averted in the Discworld novel Feet of Clay, which depicts an attempted arsenic poisoning fairly accurately.
 * Even then it wasn't to kill him either. It was to keep him from doing his normal duties.
 * V.C. Andrews' novel Flowers in the Attic has a fairly realistic version of this trope: The unwanted children's meals include powdered sugar donuts that contain traces of arsenic. Each donut contains only a minute amount of arsenic so that the children will gradually and inconspiciously die after consumption of a significant number of donuts, and the powdered sugar ensures that they won't taste the poison's bitterness. The children unwittingly hasten the death of one of them by giving him all their powdered sugar donuts because he won't eat much else from the meals.
 * Averted in Madame Bovary by Gustave Flaubert. The eponymous character attempts to kill herself by swallowing a large dose of arsenic. Instead of instantaneous death, Emma Bovary endured several days of intense and gruesome illness before she finally died.
 * Note that this is completely in-character for Emma, who has lived her entire life believing herself the heroine of cheesy romance story, while unfortunately only being the (arguable) heroine of a painfully realistic and extremely cynical one.
 * Shakespeare was in love with this trope. It seems like half his tragedies involve somebody getting poisoned with "the deadliest poison known to man".
 * Hamlet is particularly striking. Laertes returns from abroad to find that his father had been murdered. Fortunately, he just so happens to have purchased a phial of Super Poison that he's going to use for the old "dueling with poisoned swords" trick. I guess that poison was available at souvenir stands all over France, next to the T-shirts and shotglasses.


 * Surprisingly common Super Poison also appears in Romeo and Juliet. Although as that poisoning was voluntary it probably wouldn't have mattered if it had had a distinctive smell or taste.
 * In A Song of Ice and Fire, which has fairly medieval technology, the 'tears of Lys' are a poison that effectively duplicates the effects of a harsh fever, leading to an apparently natural death. However, it's stated that the death takes some weeks, and it may well require repeated dosages. More messily, another poison causes symptoms which resemble anaphylatic shock or choking/suffocation—but the poison is stated to have magic in it, and it may have been sourced from an order of shapechanging assassins, so it may be justified. Other than that, all poisons are detected by food tasters, kill over time, or are not used to kill at all; for example, one character doses another with a poison that leaves her indisposed for a day or two so that he can work uninterrupted.
 * Addressed and averted in Simon Spurrier's Contract: the main character and hitman Michael Point drills holes in his bullets, and notes (in monologue) that conventional wisdom suggests that he fill them with poison so that his targets will die even if they were only winged. However, he goes into great detail as to why most poisons are ineffective for this kind of use, too expensive, or just plain unattainable; eventually, he decides to fill each bullet with a thousand milligrams of pure heroin - dissolved with a drop of lemon juice - in the hope that even a nonlethal shot will result in a fatal overdose.
 * Subverted in Best Served Cold by Joe Abercrombie. The opening scene with the master poisoner Castor Morveer starts with him telling his apprentice about the "King of Poisons", a toxin that is both completely undetectable and impossible to build up an immunity against, and should only be used against someone who is protected against all else to keep the secret. However
 * Averted in the Belgariad, where there is no such thing as a symptomless poison, at least to someone who's familiar with them. In fact, most poisons kill in somewhat over-the-top manners. The closest there is to a "perfect" poison, thalot (a guaranteed kill even against magic, because it poisons everything in the victim's body), takes several days to finish off the victim.
 * Subverted in Dune: House Atreides, where Hasimir Fenring poisons Emperor Elrood Corrino IX at the request of the Emperor's son Shaddam with a chaumurky (poison that goes in a drink) that takes two years to work. The poison requires constant consumption of spice beer in order to work. Fortunately for the assassin, Elrood loves spice beer. Also, the effects of chaumurky become apparent within weeks, as the aging Emperor slowly begins to exhibit symptoms similar to senility. Given his advanced age, nobody suspects foul play.
 * In Robert E. Howard's Conan the Barbarian story "The Tower of Elephant" Taurus kills several lions by blowing a powder at them.
 * Tom Clancy's The Teeth of the Tiger uses this form of instant undetectable poison.
 * The short story "The Poison Necklace" revolves around the eponymous necklace, the jewels of which are crystallized forms of various extremely toxic substances. The deaths it causes are nearly impossible to diagnose because the necklace looks entirely harmless, and the effects don't match any known poison. It was created solely as a science project, handled with gloves and kept under a bell jar, never meant to be worn.
 * Subverted in Isaac Asimov's The Naked Sun. A poisoning is attempted, but any kind of murder, let alone murder by poison, is so unheard of on Solaria that the attempt fails. The would-be assassin used too much poison, and the victim vomited it up before it could kill him.
 * Done right for once in Codex Alera.  was fed small amounts of poison for years by , allowing it to gradually build up in his system. The effects of the poison are so slow that the victim thinks that the discomfort and pain are merely signs that he's getting old.
 * Subverted in Isaac Asimov's The Naked Sun. A poisoning is attempted, but any kind of murder, let alone murder by poison, is so unheard of on Solaria that the attempt fails. The would-be assassin used too much poison, and the victim vomited it up before it could kill him.
 * Done right for once in Codex Alera.  was fed small amounts of poison for years by , allowing it to gradually build up in his system. The effects of the poison are so slow that the victim thinks that the discomfort and pain are merely signs that he's getting old.

Live-Action TV

 * The TV forensic show Forensic Files—which focuses on real-life law enforcement officers solving real-life crimes without Hollywood Science forencics—throws this trope up in the air in several episodes where a person has survived doses of poisons magnitudes larger than it would take to kill a person simply because they had been given small does over periods of years and had built up a tolerance to it. Cut to a graph of "Here's what would kill a normal person" and, six inches higher on the graph, "Here's where his/her levels were".
 * Subverted in The Tenth Kingdom, where it was established that the Wicked Queen killed Snow White's mother by slowly poisoning her as her handmaid, then married Snow White's father and did the same to him. The same was done to Prince Wendall's parents by the new stepmother.
 * Subverted in an episode of CSI: Crime Scene Investigation. The CSIs spend most of the episode looking for the instant poison that likely killed a high-stakes poker player. Grissom realizes at the end that it was a combination of factors—a "lucky" bullet stuck in his leg he never took out, plus a daily regimen of chocolates grown in a country where the cars use leaded fuel—that built up to create a serious medical condition. The guy was 'poisoned' with eye drops which in a regular person would have simply induced diarrhea. The lead in his system made the eye drops deadly.
 * I, Claudius, has a number of poisoners, all of whom dose their victims over a number of days to make it seem like they died of a wasting illness. One of the poisoners, Martina, advises a client against using the tasteless belladonna as a poison since it leaves a tell-tale rash, but the client doesn't listen and uses it anyway. (This later comes back to haunt said client, when she and her husband are brought in for murder charges.)
 * Both the above-quoted Twilight Zone episode and the story it's based on have "glove cleaner", "totally undetectable to all forms of autopsy". The man who sells it also sells love potions... for five dollars. He's expecting all of his customers to come back for the "glove cleaner"...
 * In the Doctor Who episode "Let's Kill Hitler", Melody Pond poisons the Doctor with a single kiss wearing lipstick containing the Poison of the Judas Tree. It's not instantly fatal, but it's perfect in the sense that it disables Time Lord Regeneration as well as killing the body. And it's non-toxic to Melody, averting the Universal Poison trope.
 * In Justified, Mags Bennett kills one of her henchman with poisoned moonshine. The unidentified poison killed him in under two minutes, and he apparently didn't detect any smell or taste.
 * Averted in Boardwalk Empire. The Commodore's maid was poisoning him with rat poison over a long period of time and in high quantities. While he is left violently ill and has to regrow his stomach lining, he still recovers to full health a few months later.
 * In the RoboCop tv series episode "RoboCop versus Commander Cash", a Mega Corp is marketing a sugary cereal that brainwashes children, the cereal box having a coded message (with orders to do their bidding) that can only be seen by someone wearing the "Ultra Specs" included with the cereal. The intent being to turn them into Child Soldiers for some unspoken nefarious plot. The key to this scheme is, the psychohypnotic agent in the cereal is undetectable unless the cereal is combined with "a common phosphorus-calcium-based household chemical" - a Techno Babble term for ordinary milk.

Radio

 * An old-time radio "Five Minute Mystery" titled The Radium Murder Case tells of a murder exposed because, according to the investigator, the poison used would instantly knock out the victim upon contact with the tongue. In this case, the poisoning was openly stated but the perpetrator attempted to claim the poisoning as a suicide.

Tabletop Games

 * Realistic use of poison in most tabletop systems is extremely rare. This is mostly due to how roleplaying systems work—poisoning someone over weeks or months is usually hard to make work mechanically, and usually won't be on the list of how Player Characters off their opponents.
 * Dungeons & Dragons has a selection of poisons that deal a random amount of ability damage to one and only one ability score over two 'doses'. These damage doses happen exactly one minute apart regardless of the type of poison used. Terms such as dosage, dilution or long-term exposure never enter into it. Poison-users *are* in danger of poisoning themselves during application, however.
 * Pathfinder, being the Spiritual Successor to the above version of D&D, has updated the poison rules in response to this trope. Poisons can now have a various onset time anywhere between six seconds and a day, and some poisons can last indefinitely. One particular poison can kill someone (by Constitution drain) over an arbitrarily long period of time.
 * Averted in Exalted; the poison rules are designed around inflicting only one die of damage per time interval (which are generally in the hours), and can only inflict a limited amount of damage per dose. Multiple doses just extend how long the poison can last, while still only inflicting one die per interval. The most dangerous poison in the game (made from the concentrated hatred of demon gods and tremendously rare and expensive) would still take about seven seconds to kill most people (and would be rather obvious about it).

Video Games

 * In the third case of Trials and Tribulations, as well as the fourth case of Apollo Justice, the victim dies from cyanide poisoning and from a (possibly) fictional poison, respectively, but in both cases the killer was more interested in having the person dead than hiding the method from the police (as far as what killed him, at least). As a result, the victim did not have a swift silent death, but instead gave full display of the poisons' physical reactions for all to witness, and the police have no trouble in figuring out what killed the victim.
 * In Achaea, a large number of poisons are available and widely used in combat. Most only cause hit point damage or a status effect, but Voyria is invariably lethal...At least it should be, if it didn't take a full thirty seconds to do its work, during which the player receives SIX warning messages describing unmistakeable symptoms (mild fever, nose bleeding, bloody vomit, heavy breathing) and has only to take a sip of Magic Antidote to instantly save himself. As everyone carries antidote with them, the only practical way to kill someone with Voyria is to prevent the victim from drinking or injecting medicine.
 * Averted in Hitman: Blood Money: one of Agent 47's primary weapons is a syringe that can be used to inject targets at the jugular or to poison food. For efficiency's sake, instead of using a single poison, a mixture of chemicals is used: sodium pentothol, pancuronium bromide and potassium chloride. Since this is the exact combination of chemicals used in lethal injection executions, the victim dies quickly and noiselessly.
 * Which only kinda makes sense. In lethal injections they use multiple IVs so the poisons don't mix beforehand and undergo a process called precipitation. A fancy way of saying they get all waxy and won't go in. And it can still take two hours for the victim to die. It would work better to just use one of the first two (the more fast acting drugs) and strangle the person after they pass out.
 * Probably the reason that 47 carries around a reel of piano wire. However, Blood Money's use of poison makes more sense than the previous game, Contracts: in several levels, you're forced to look for poisons in the surrounding area and dose people's food or drink with it, and weedkiller or rat poison aren't exactly painless or quiet.
 * It should be noted the the poison in Blood Money isn't undetectable; kills with poison count as regular kills rather than accidents.
 * In Final Fantasy Tactics slowly poisoned his father over many years, which the rest of the family mistook for an illness.
 * Dragon Quest VII has the whole debacle in Verdham where Kaya is slowly poisoning her husband. The poison she uses is a powder which she keeps in a vial around her neck; her husband is convinced it's his medicine, and you have to get the bottle away from her and its contents tested to prove otherwise.
 * Dragon Age Origins has a whole skill based around the creation of poisons and toxins to coat weapons with. These work instantly.
 * The same goes for The Elder Scrolls: Oblivion. There are also instantly fatal poisoned apples you can sneak into people's inventory, if they don't have any other food in there, they will eat the apples eventually and die.
 * In an ending cut from Jade Empire, Sky dies from drinking poisoned wine.

Web Comics

 * Minions At Work: An early retirement plan with a fresh, minty after-taste!
 * In the Jack Chick tract Party Girl, a man who drinks a poisoned drink dies in less than four minutes.

Web Original

 * On their wiki, the PPC refers to this as "Ye Olde Poisonous Poison."

Real Life

 * Genghis Khan's father is believed to have been killed by drinking poisoned milk during a meal with rival Tatars.
 * The Ice Man said that he would kill people by putting large amounts of cyanide in drinks, spilling it on them, and walking away.
 * Karen Wetterhahn died after exposure to a tiny drop of dimethyl mercury on her gloved hand. However, the death was long and drawn out. And it wasn't untraceable either.
 * The rumors spread about Lucrezia Borgia by her family's enemies often included a reference to a poison she made called "la cantarella." Even if the Borgias did have people poisoned, this particular substance was alleged to be such a perfect poison that it could not in fact have been real.
 * The real-life poisons abrin and ricin are both easily obtained from common ornamental plants, very deadly, and difficult to trace (the assassination of Georgei Markov was not traced because of the ricin, but because of the capsule used to deliver the poison ). Neither kills as quickly as the trope demands, but they're as close as real life gets.
 * Alexander Litvinenko, a prominent critic of then-president of Russia Vladimir Putin, was the victim of quite possibly the most unsubtle murder by poisoning in living memory when someone -never conclusively proven but widely believed to be a Russian intelligence officer- sprinkled a highly radioactive substance over his food at a London sushi restaraunt. The isotope used is one of the most deadly substances known to man, and investigators traced the smuggling of it by following the prominent cases of radiation poisoning that it left in its wake.