A wide variety of characters behave as if they are actual police officers and detectives or otherwise overstep their bounds, particularly the Amateur Sleuth (Murder She Wrote) and technicians (CSI, Quincy, Crossing Jordan).
Real police tend to take a very dim view of this practise. However, as was once said of Star Trek's habit of sending the command staff into dangerous situations, if you're paying for the stars, you damn well better use them.
If you're looking for the offence of impersonating cops, look no further than the Bavarian Fire Drill.
- Two Thousand AD: Cover Art for one issue showed a little kid who had dressed up like Judge Dredd, presumably in an act of hero-worship. Dredd was also in the picture, saying: "Impersonating an Officer. Sentence; fifteen years in the Juve Cubes." Yes, he was handcuffing the kid at the time.
- 8mm: The private eye protagonist poses as a government investigator. As he's working for a highly-paying client, he thinks it's worth the risk. Towards the end of the movie he claims to be a police officer when ringing around the hospitals looking for the man he stabbed, but by that stage he's so personally involved in the case he doesn't give a damn.
- In Jumper, the Ancient Conspiracy seems incredibly powerful, when first introduced with members appearing to be CIA, FBI, etc. Later in the film, it becomes clear they're just a bunch of well-funded vigilantes who carry around a bunch of fake I.D.s.
- Captain Jack Sparrow's sentencing at the end of the first movie includes "Impersonating an officer of the Royal Navy" and "Impersonating a cleric of the Church of England."
- This happens a few times in the Terminator series. The bad machines (and occasionally the good ones) dress up as cops to get where they need to be without causing chaos on the way.
- Both Maniac Cop and Psycho Cop has killers who dress like cops to get near their victims.
- An especially scary version in the film Copycat, where the killer disguises himself as a dead police officer in order to escape detection by another cop.
- It's believed that the above example is a reference to a similar scene in The Silence of the Lambs, in which Hannibal Lecter disguises himself as an injured police officer in order to escape custody.
- Dirk Gently's Holistic Detective Agency: Dirk does this as part of the workings of his Holistic Detective Agency when he has a mystery that actually interests him rather than one that involves tricking old ladies into letting their cats loose. The local inspector Sergeant Gilks takes a rather dim view of this... along with Dirk's tendencies to be involved in highly peculiar situations that Gilks does not like very much in the first place, as well as his habits of removing or obscuring evidence...
- Angel: Angel would occasionally walk right into crime scenes and start ordering cops about as if he ought to be there, then demand that one of them give him a run-down of the crime scene. He, however, knew that this was a Bavarian Fire Drill and expected to get in trouble if called on it.
- Averted in Torchwood, in which they do have authorization to be at crime scenes, but the police aren't happy about it (it doesn't help that they're not quite sure what Torchwood actually does). In one episode, Jack has to call the police for help when everyone but Gwen winds up locked in the base with no power; the officer who takes the call puts it on speaker and calls the entire station over to mock them.
- In almost every post-revival episode of Doctor Who where the Doctor has any interaction whatsoever with human authority, he manages to take charge of said authority within about thirty seconds. Assuming the authority is not the villain, of course. UNIT, long used to the Doctor, will salute him but don't always let him take charge immediately.
- The guys on Hustle do this with some regularity, Mickey even makes his cruise from England to Australia by imperonating a Royal Navy Officer.
- Similarly to Hustle the team on Leverage frequently portray law enforcement officers as part of the con. Notably, a pair of real FBI agents believe that Hardison and Parker are on undercover assignments when they are in fact thieves.
- Happened in Ally McBeal once when two of the attorneys were present during an arrest. They were promptly arrested as well.
Fish: What was I supposed to do? Yell "Lawyer"?
- Tracker uses this extensively, with Mel and Cole using old police badges (from the walls of the Watchfire Policeman's bar) to pull off the trick.
- Supernatural: The brothers have this down to an artform: the older brother Dean even has an entire box filled with fake IDs, just in case he needs it (Which he frequently does). If anyone questions their authority or jurisdiction, they can give him/her the number of their 'superior' to confirm who they are. Their friend Bobby has a bank of phones in his home that these numbers connect to and he then impersonates the appropriate agency (FBI, CDC, Homeland Security, etc).
- In Castle, although merely a shadowing writer Castle has been given a lot of responsibility within the unit, including questioning witnesses and examining evidence and crime scenes (albeit always with Beckett observing him). Lampshaded in one episode where he excitedly calls a newspaper to acquire confidential information after a brainwave, only to stop when they ask him who he is and hand the phone over to Beckett, sheepishly admitting that "I sometimes forget I'm not actually a cop." Later seasons offer a Hand Wave for this by having the detective characters refer to Castle as a 'consultant', suggesting the department actively employs him on a semi-official basis to consult for them rather than just letting him tag along as a writer.
- In an episode of The District, a rapist working at a shop that repaired Metro Police cars used access to official cars and a police uniform to get close enough to intended victims to capture them for the assault. This didn't do any favors for the real MPD (particularly one officer who bore a superficial resemblance to witness descriptions of their attacker), when news stories about the rapist mentioned his MO. Sergeant Brander even wound up being shot by a panicking motorist stopped for a traffic violation, though he was wearing a bulletproof vest under his uniform shirt at the time, so he wasn't harmed.
- Threshold: The team actually have authorization to impersonate agencies whose existence is not classified. The FBI is the most common, but they've also used the FDA and Department of Agriculture.
- An episode of Third Watch had the cops hunting for a pair of rapists who would pose as cops so that they could pull women over and assault them.
- As mentioned below in the Real Life section, this is a real tactic and has been used by people ranging from Anders Breivik (the Oslo gunman) to Ted Bundy. Check the badges, people.
- A serial killer on Cold Case employed this trope to lure his victims away with him.
- New Tricks: Brian, Jack and Gerry are retired police officers and are usually pretty good at identifying themselves as such. However, they do work for the police department as investigators so they have the official authority to question people and access police records.
- Patrick Jayne of the Mentalist will usually inform people that he is merely a consultant and not an actual police officer. However, when he deems it necessary he has no qualms about letting people think that he is a full CBI agent.
- Married... with Children: Al Bundy donned the uniform once so he could be part of the show "COPS".
- Parks and Recreation: In an attempt to coerce a confession out of local juvenile delinquent Greg Pikitis, Andy says he is FBI Agent Bert Macklin. The next time we see "Bert" and Greg, Greg has him near tears.
- In Sherlock, the titular character has an entire box full of IDs that's he pickpocketed from Lestrade "when he's being particularly annoying."
- Phoenix Wright: Ace Attorney: Phoenix does this constantly, and often swipes evidence from the scene of the crime. However, it's implied that the law in his world differs from real-world law on this point; on several occasions he's shown receiving assistance from the police during his on-scene investigations. There's a very odd line late in game 1 where Phoenix says that he's not supposed to do that. Really? Because it didn't seem to cause you any trouble with the police all the previous times you did it. Quite often, he even ends up doing their work. Especially including using the nifty gadgets for them.
- Fillmore!: The Disney Channel show is one giant use of this trope. It works in this case though, as the Safety Patrol is equivalent to police officers as the school is equal to a city. The scale keeps the show on homage level, not really impersonations.
- More ominously, a tactic often used by criminals hoping to entrap a victim—Ted Bundy and the Hillside Stranglers would frequently employ it.
- This trick was used in a horrible, horrible way by the Norwegian right-wing terrorist Anders Breivik, who set off a bomb in downtown Oslo, then travelled to the island of Utøya (where the Norwegian Labour Party's annual youth camp was taking place), dressed as a police officer. Once there, he used his Impersonation of an Officer to gather a lot of people in one location, gave a talk in which he "informed" them about the earlier bombing, then started mowing down his audience with the heavy guns he had with him. Eyewitness accounts describe people who had run from the sound of gunfire running towards Breivik, because they thought he was a police officer who could protect them - only to be gunned down mercilessly. End result? Seventy-seven dead, most of them teenagers.
- An especially horrible subversion with real police officers who have used their uniforms and badges to intimidate and harm people.
- A common method of Social Engineering. Perpetrators often pose as network/IT staff and ask for usernames and passwords, claiming to need them for troubleshooting.
- This is generally countered by actual IT staff repeatedly telling everyone to ABSOLUTELY NEVER give out passwords. In some cases people respond to the emails telling them to never give out their passwords with their passwords.