Be as Unhelpful as Possible

""Suspects lie because they have to. Witnesses lie because they think they have to. And everyone else lies for the sheer joy of it.""

- David Simon, Homicide: A Year on the Killing Streets

In a Police Procedural, interviews are short and sweet, and the characters try to give as little useful information as possible. This is done to keep as many of the characters as possible suspects for as long as possible, but often falls flat. In order to give an excuse for this unhelpful behavior, the characters that didn't do it often have a Big Secret. In cases of You Didn't Ask, they'll answer your questions and give you nothing more, dragging the whole thing out.

One need not be a suspect to be as unhelpful as possible. Almost never, in the entire history of television, has a victim's family been interested in finding the actual perp once a Red Herring suspect has been identified. If a suspect has been wrongly convicted, the family will occasionally go as far as to actively hinder the investigation, even when it is obvious that the real killer is still at large, preferring the "closure" of a conviction. This is one of the rare cases of a cop show mirroring real life.

This trope is sometimes inverted, rather than subverted. The guilty party has been providing information to clear his name, expressing support for the investigation at every opportunity, and generally being too helpful—all in an effort to deflect suspicion. (CSI is fond of this variation, as is Scooby Doo.) Another alternative is Infraction Distraction, where the guilty party confesses to minor wrongdoing to cover up major wrongdoing.

See also Perp Sweating, Only Bad Guys Call Their Lawyers.

Anime & Manga

 * In Monster, Tenma averts this until Lunge, of all people, tells him to keep silent to hinder the investigation.

Film

 * In Once Upon A Crime several of the main characters lie outrageously and try to create alibis for each other about the murder they're caught up in. They're all innocent but due to several bizarre twists of fate (such as one of them stealing a suitcase that contains the body) they find themselves implicated, and fear that unless they have some kind of alibi, they'll be sentenced no matter how innocent they are.
 * In Bad Lieutenant Port of Call New Orleans, the investigation of a quintuple murder is stymied by the fact that no one they interview wants to answer any questions. This has a much simpler justification than most examples of this trope: all of the interviewees know who committed the murders, and they're terrified of him.

Live Action TV
"David: What happened immediately after the foot-running-over moment? Lee: "Ow!" David:Can you roll that forwards? Lee: "Ow! That was my foot!""
 * When a member of CSI indicates that the husband is always the first suspect when a wife is murdered, the husband's response is typically "You think I did this? This interview is over!" While common sense might dictate giving all the information to clear your name as quickly as possible, it's actually more pragmatic not to. In Real Life, police expect ordinary people to get angry when accused of crimes they didn't commit.
 * This is mentioned in The Lives of Others. At the beginning of the movie, a Stasi officer explains that if you question an innocent man for several hours, he will get seriously pissed off and start screaming at you. On the other hand, someone who's guilty will try to be helpful and cooperate, no matter how long the questioning.
 * And of course it depends on the quality of your police force. There is such a thing as police fabricating evidence.
 * Also occurs in Lie to Me. They realize that a suspect is innocent when he gets enormously angry at various accusations rather than trying to defend himself. Lightman points out that most men do not like being accused of rape.
 * The one exception to the statement that "victims' families lie" occurs in Life On Mars, where the parents of a murdered schoolgirl . Of course, they are still as unhelpful as possible, since being helpful would make it obvious that they were blackmailing the police.
 * Befitting its reputation for being a Medical Procedural, House features patients who, even in the face of their impending nasty and painful deaths from various illnesses, will still lie to protect their pointless secrets. Usually happens for one of four explanations that keep popping up: a) the patient wants to keep a secret that would ruin him or her, b) the patient doesn't know the secret, c) the patient doesn't realise that the secret is connected to his illness, and the overriding d) the patient doesn't believe their life is in danger because, hey! They're in a hospital!
 * There are also cases where some immediate family member will be the one keeping the secret, usually for one of the same reasons above.
 * This was actually later lampshaded by a patient who remarks "You know what my favourite time to lie is? When my life's hanging in the balance."
 * It doesn't help that in at least one case they forced the secret out of the patient in front of his father, who was the only person who cared about the secret. Asking people to reveal secrets is a lot easier if you provide some measure of confidentiality. You know, as doctors are legally bound to do. There are exceptions, but whatever the person is concealing rarely qualifies.
 * Lampshaded on Bones, where Booth points out to a film student suspect that this is the point where the innocent person helps, and the guilty person asks for their lawyer. The kid helps. At the end of the episode, they know they've got the right guy when they present him with evidence and he...asks for his lawyer. He's not actually telling the truth, just manipulating the student's Genre Savvy; on several occasions in the show, the innocent parties have called a lawyer, sometimes to protect some other secret not related to the case.
 * Played with on Bones again later, during the coma dream episode. Everybody believes Booth is the killer... and they're all being as difficult as possible to protect him. Of course, none of them believe him when he says he didn't do it, and they refuse to stop, even when he asks them to.
 * On one Law and Order Special Victims Unit episode, a man is accusing three women of raping him. The ADA specifically asks him if there's anything else he'd like to tell her, and he looks uncertain for a second and says no. Turns out in court that he tried to sue his rapists, making him look like a golddigger. He was just trying to get information on them, but the ADA still rips him a new one. Of course, Cabot was holding something of an Idiot Ball herself; what type of ADA doesn't check the records of a star witness to find something the defense can use to discredit them?
 * The Shield uses the normal example straight many times, but also notably uses the Inverted example as well. Dutch and Billings are investigating a serial child rapist, and Billings figures out that the child shelter manager who has been extremely helpful has been *too* helpful. Yup, turns out it was him.
 * Another Inverted example occurs when Dutch is investigating a routine shooting, and asks three suspects for gunshot residue tests to see if they've fired a weapon. Two of the suspects refuse, and the third agrees. Turns out, the third guy did it. He didn't refuse the test because, "Well, you said it was a government test, right? I figured...how accurate could it be?"
 * Actually, it was two suspects, and they both agreed to the test. The one not in the above quote was a cheapskate, and asks Dutch if the test will cost him anything. Dutch's response: "Only if you're lying."
 * Averted in Numb3rs, when a rich father finds . He rushes into the station, takes one look at the TV paused on a shot of his daughter, and says he'll do anything he can to help the police. When the FBI Agent remarks that he's being remarkably helpful, he says that the sooner they get his daughter home safe, the sooner he can prepare a defense.
 * Thankfully averted during the serial killer storyline on Blue Heelers in 2005. When the (innocent) prime suspect, a psychiatrist, is talking to the detective socially, he realises midway through their conversation how much of the evidence points to him: he lives across the street from the first victim, he runs the support group for child sex abuse sufferers that victims 2 and 3 belonged to, he used to be a priest (tying in with the religious symbols next to the bodies), he has a criminal record for domestic violence and he has no alibi for any of the nights on which the murders occurred. He immediately chooses to make a statement, and, once cleared, helps them catch the killer.
 * Although not a crime show, Lost frequently maintains its mysterious mysteriousness with this trope. The characters repeatedly encounter people who have very useful information that is critical to their survival but refuse to share this information even when it would be a really, really good idea. These kinds of characters often make cryptic references which indicate they have a deeper knowledge of the situation, but the protagonists never bother to ask them direct questions.
 * Inverted in an episode of The Sentinel. Ellison is trying to track down a serial killer, and a profiler is brought in to tell them about the psychological make-up of the killer. It turns out near the end of the episode that the profiler was the serial killer. He had killed the real profiler and took his place, and provided them with completely accurate information about himself just to screw with them.
 * Try counting the number of times "No comment" is said in the interrogation room on UK crime drama The Bill.
 * Refreshingly averted in one episode of Castle, where the suspect (who they are absolutely certain is the killer) gives them absolutely everything they need, over the objections of his lawyer. "Save the defense for when I actually kill someone, all right?"
 * It is something of a Running Gag commonly done by Lee Mack on Would I Lie to You? though other panelists certainly use this as a strategy to buy time.

Video Games

 * This is a large part of Ace Attorney, particularly in the later games where you have to break the "Psyche-Locks" that represent their secrets by shoving evidence to them.
 * And subverted by Wendy Oldbag - the Locks say her secret's buried deep, but she wants to tell - three of them break in one go, and she gives you the last one free because she's so droolingly into the case's victim.
 * Averted in Ace Attorney Investigations with, who is quite possibly the most helpful, least secretive and least incorrect witness in the whole series.
 * Which is extremely effective because Genre Savvy fans of the series will instantly assume is the real killer just for that, plus his  that'd be perfect for a confession freak-out.
 * Borderline example: in Mega Man X 4, the Reploid military force Repliforce is accused of attacking and bringing down a sky colony, causing millions of deaths. Uncharacteristically of them, the Maverick Hunters try to get Repliforce's members into custody peacefully so they can investigate and possibly clear their names (instead of blasting them into scrap at first sight), but they're too proud to disarm and state they will fight to the death before they would ever put away their weapons. They're labeled Mavericks and all but annihilated, afterward, as a result.
 * Of course, the Repliforce crosses the Moral Event Horizon by turning their peaceful rebellion into a violent one. Reasonably, the hunters (X and Zero in this case) try to talk Repliforce out of their rebellion, but everything's gone too far. This is the event that ends up making X seriously question the inherent violence in the Maverick Hunter system (previously, he was a reluctant, but willing fighter), and gives Zero a Heroic BSOD, both of which come back to haunt them.
 * In L.A. Noire, everyone is holding out something from you. Everyone. Even people who want to be helpful (though in many cases, it's not a question of them purposefully withholding information, but rather directly answering the question, requiring a follow-up on a different track).
 * Example in an early interview: When talking to a witness who is otherwise totally uninvolved and has nothing to fear, she'll still lie to you. If you catch her out, she admits that she was holding back some info in hopes of selling it to the newspapers.

Real Life

 * If you are arrested in the United States any good lawyer will advise you to remain silent, and wait for your lawyer to be present, even if you are completely innocent and think that talking to the police will help convince them of your innocence. Talking to the police can not help you avoid being arrested (they aren't showing up at your door to decide whether or not to arrest you—they're showing up at your door because they've already decided) and can only be used against you. Some details are discussed here. This doesn't apply where staying silent may harm your defence (that is to say, when it hurts your credibility in court to have not told vital testimony to the police).
 * In Canada, you do not have the right to have an attorney present while being questioned - but you do have the right to speak to one before being questioned, and you always have the right to say nothing.
 * Stop snitching. Rapper Camron infamously said in an interview that if he knew he were living next to a serial killer, he'd move rather than go to the police - or help them in their investigation. And remember, this is the same industry that complains about the fact that the murders of Tupac Shakur, The Notorious B.I.G. and Jam-Master Jay were never solved.
 * Not everyone in the industry agrees with him though (especially the friends and family of the three murdered rappers that were mentioned).