Obstructive Vigilantism

Everyone knows that the cops are on your side, and if you let them handle things, then everything will work out, right? Just tell them what you witnessed to get them on the trail, and then the perpetrator will be caught and sentenced. Well, some people think differently. Sometimes, a character might go so far as to lie about what he knows in order to take the law into his own hands. Worse yet, the bad guys might do this, too, and want to settle a score.

When it comes to the alleged good guys, this is usually done to prevent a character from being tied to any terrible accident that the criminal encounters. Maybe there's been a crime. The police go around asking people whether they have seen or heard anything, but no one saw anything, no one heard anything, and some people had no idea a crime took place. But after the police finish their investigation and leave, someone goes and tells the local Vigilante. Or maybe he is the local vigilante. Another version involves a cop, superhero, military officer or anyone else who is part of some sort of law-enforcement agency who decides to lie to the other members of their group and pretend he knows nothing, in order to kill the perpetrator, instead of having to "do the right thing" and give the perpetrator a trial. He might even be somewhat law-abiding, and is simply stalling to get more evidence.

Anime and Manga

 * In the Pokémon Gold/Silver manga, a part at the beginning of the game -- where the player is asked to give the name of his rival by reporting it to the police (in the original, he tells you his name for no reason; in the DS remakes, the Player Character gets a look at his trainer card) -- is portrayed as Gold misleading the police so he can take the rival down himself.

Film

 * In Death Wish II, Paul Kersey tells the police he didn't get a good look at the people who attacked him and killed his daughter and housekeeper. He then goes out and.
 * At the end of The Departed,.
 * In Stop or My Mom Will Shoot, the titular mom is not telling all the details so that her son can investigate.
 * In Vigilante, after a woman is raped in her building, an older woman tells the police that she did not see who did it, despite passing the rapist on the stairs. She then gets into a van with Nick and the gang, driving around town looking for the rapist.
 * In Death Sentence, the protagonist manages to get a good look at the man who killed his son but decides to drop the charges when he discovers that he would only get 3 to 5 years of prison, with the aim of killing him himself. This backfires badly.

Live-Action Television

 * In an episode of Breaking Bad. Tio Salamanca goes in to testify against Jesse, but he doesn't actually tell the cops anything.
 * Dexter, being a Serial Killer Killer who is also a detective, will often falsify, lie about and steal evidence so that criminals go free, and he can enjoy murdering them later.
 * This shows up a few times on the original Law and Order.
 * Replacement Scrappy Nick Falco shows up after his short run as a suspect and his determined efforts to clear his name repeatedly pooch the investigation.
 * One episode sees a war widow's infant child die in a fire while they're sleeping at a recruitment office that gets firebombed. Activist vigilantes repeatedly aid the investigation and the police are very, very grateful for their very helpful help.

Video Games

 * In Max Payne 2, one of the graphic-novel cutscenes has Max contemplating this, but he ultimately decides to come clean. Sort of.
 * In Mass Effect 2, Cerberus feeds the authorities false information on at least one and probably multiple occasions to give Shepard a chance to get in and investigate sensitive situations before anyone else shows up.