Many countries, such as the United States, require police officers to gain permission from either the homeowner or the courts before they collect evidence or enter a residence to investigate. Writers often completely ignore this in favour of an interesting narrative. Ignoring the rules for evidence collection and the limits (legal or otherwise) of hospitality is a line that both the Dirty Cop and Cowboy Cop will cross in service to their desires. Any time the By-the-Book Cop is willing to cross this line is a distinctive moment for that character, possibly Character Development into a different type of cop.
Cops who cross this line may try to justify their actions before or after the fact with a Blatant Lies excuse of hearing a call for help, finding the door open when they arrived, or telling the suspect that they will be asking a routine questionnaire (most probably confirmation of name, status, and minor questions about the case at hand). They can also justify Perp Sweating a suspect without their consent, using nonsense like Conviction by Contradiction (provided by, for example, the ire of the suspect upon the violation of his rights) to continue their examination past what is legally allowed. In all cases, the cop breaking the rule and at least one other character is aware of the laws regarding evidence collection, but those laws are being disregarded for the sake of the story.
It is the duty of Internal Affairs to discover and administer consequences to cops who cross this line, but this rarely comes up, except when the story needs Padding, or a Halfway Plot Switch, when the second part of the episode is about this sort of misuse of authority.
Generally in democratic societies, there are only very limited exigent circumstances where a warrantless entry can be done. One of these circumstances is "Hot Pursuit"; i.e. if a cop is chasing a suspect and the suspect runs into a house and slams the door closed, the cop does not have to stop and get a warrant to enter. The Other Wiki has an article on Hot Pursuit. However, if you are a member of the Armed Forces, or on a military installation, your person, your car, your belongings, and your quarters can be searched at any time, for any reason, without a warrant. Military personnel give up this right when they join — or are drafted into — the military. Visitors to military installations should pay close attention to the signs at every gate which clearly state that all visitors are subject to search without warrant or warning. If you enter the base, you've agreed to those conditions.
- Played straight in Zootopia. When Judy and Nick reach the limo service business holding the car they are tracking, they find it closed and Judy doesn't have a warrant. Judy prepares to give Nick back the recorder pen she was using to blackmail him but tosses it over the fence at the last second. Nick climbs the fence to get it, only to find that Judy has burrowed underneath the fence and beaten him in with this excellent response:
Judy: The thing is, you don't need a warrant if you have probable cause, and I'm pretty sure I saw a shifty lowlife climbing the fence.
- In Bad Boys, Mike Lowrey and Marcus Burnett are discussing that there appears to be no one home at the house of a suspect, and Mike leans in and opens the door, saying out loud "I tripped, and the door just opened. It's like they wanted us to come in."
- Beverly Hills Cop: This is Axel Foley's modus operandi (especially because he's a Detroit cop, and thus has no jurisdiction), but one example in the first film stands out; he makes a Lampshade Hanging that he has no probable cause to check Maitland's warehouse for drugs (to keep Officer Rosewood from following him), and pulls a Bavarian Fire Drill on the guards involving Audit Threats when they think it's wrong for him to be there.
- The Brute Man: A fugitive breaks into a blind woman's apartment to hide. He asks her for help, saying that "some men" are after him. She hears a knock on the door and tells him to hide in another room. When she opens the door, three men barge into her home without even identifying themselves as police officers (although two were wearing uniforms, they didn't try to show her a badge or even offer any explanation), and she tells them that she didn't see anyone. The leader then orders his men to look in the woman's bedroom (with no search warrant, no explanation offered to the woman), but the fugitive escapes through a window. Later in the film, the police arrest her for harboring a criminal, but she claims innocence because she didn't know he was a criminal and didn't know the officers were policemen since they didn't even identify themselves.
- Dirty Harry: Under pressure to rescue a girl Buried Alive, Detective Callahan breaks into the home of serial killer Scorpio on a tip and tortures a confession and the hostage's location out of him. The confession and the murder weapon he collects are inadmissible, Scorpio walks, and on top of it all, he is too late to save her.
- Smokey and the Bandit: Over the course of three films, small-town Sheriff Buford T. Justice uses and abuses the "Hot Pursuit" rule to the point of absolute insanity (saying "I'm in hot pursuit!" is his Catch-Phrase, even), chasing after Bandit through multiple states on charges that are either trumped up or not even done on his jurisdiction. When other law enforcement tries to ask what the hell is he doing, he will tell them to get out of his way.
- Cowboy Cop Tom Ludlow in Street Kings invokes this after trailing kidnappers to their hideout, and ambushing them unannounced. When being debriefed by his captain, he lies, claiming "exigent circumstances" as his rationale for busting in without a warrant, backup, or even an announcement.
- In a Made-for-TV Movie called The Supercops, one of the heroes goes into an alley behind an apartment. His partner knocks on the door of the apartment, and the guy in the alley yells "Come in!".
- On the first two Death Wish films, this happens to Paul Kersey. Even more, both times his house is broken in and searched is by the same cop (and on the latter movie he has absolutely no jurisdiction because he's an NY detective and Kersey is living in LA — also, he uses the moment he breaks in to try to intimidate Kersey's Girl of the Week into convincing Kersey to stop, an even bigger legal no-no if the woman decided to report it). While the police has suspicion about Kersey being the vigilante they are looking for on the first film, they have no evidence up until said break-in is done and the detective finds some bloody tissues to compare with the blood on a knife that Kersey had been wounded with. This is all presented as evidence that the New York police is more concerned about looking efficient that they are with actually being efficient, and thus go after anybody who dares make them look bad, legality be damned.
- Averted in A Brother's Price: The Princess Rensellaer herself finds herself patiently waiting for permission to enter a simple farm. Captain Tern thought it advisable, as the farm is guarded by heavily armed children, and she doesn't want to have to kill them for attacking the Princess.
- Jinx High: When Diana, Larry, and Mark find Fay Harper's ritual space, Mark picks the lock on both the gate across the road and the building itself. Subverted in that while Mark's a cop (outside his jurisdiction, but still a cop), it's not like anything will be going before a judge — the group just wants to sabotage any spells the owner has prepared and drain off the owner's stored Mana.
"Boy, I'll tell you, it's amazing how careless people are, leaving their gates unlocked like that."
- An episode of All in the Family has Archie getting arrested for posession of a weapon without a permit when he lets a policeman into his house, but the case is thrown out of court because the officer didn't have a search warrant. The plot is meant to deliver an Aesop about why cops have limits on how they can enforce the law. A case of Hollywood Law causing a Broken Aesop, since police officers don't need a warrant to search a home when they have the homeowner's consent to entry.
- Sometimes used on Bones where Booth will say "Did you hear that?" to Brennan before breaking down the door. Other times he'll mix it up, telling Brennan "if anyone asks, we found the door open."
- In an episode of Castle, Esposito and Ryan are tracking down the owner of a safe deposit box, no one is answering the door. Ryan says "Did you hear that?", Esposito immediately follows with "Yeah...", fakes a "help" in a female voice, and they barge in... to find a dead body.
- Lieutenant Columbo is a perfect example of the second variety of the Trope — he continuously pesters the suspects by appearing anywhere they are (work, home, middle of the street, wherever) and claiming he is just going to "ask some questions" — that start as random nit-picking and become Perp Sweating by annoyance as the episode continues. He has also grabbed evidence and kept it to himself (disregarding the chain of evidence completely) to confront a suspect with it later on. At least in one episode, he explicitly said that the suspect's hostile response to this modus operandi was leading him on the right path, because he "struck a nerve".
- Played straight in an episode on a British cruise ship, where a murder has occurred while Columbo and his wife are vacationing. Knowing that he's a police detective, the Captain of the ship asks for Columbo's assistance. Columbo does so, but makes it clear he is only capable of assisting and has absolutely no authority or jurisdiction on a cruise ship on the high seas. A crew member is a suspect, and Columbo says they'll need a search warrant to check his cabin for the murder weapon. The Captain states that he doesn't need a warrant to search a crew member's quarters (Truth in Television, he doesn't) and orders his first officer to immediately search the cabin.
- Zig-Zagged in an episode of The Commish when Tony is faced with an illegal search dilemma during the hunt for a stolen baby. He's reasonably sure he's at the right house, but he can't wait for a search warrant. If he goes in without a warrant, the search will be illegal and the perp will walk, but if he waits, the baby could die (it has a rare condition and needs its medicine). He tries to play the "did you hear that?" game with his supporting officers, but realizes he's too honest for that. He busts in anyway and finds the baby.
- Deconstructed in the Elementary episode "Tremors". Facing an inquiry into the events leading to Detective Bell Taking the Bullet for Sherlock, Sherlock claims they have encountered an unusually high number of open doors, and at least one puppy and television that each sounded like someone calling for help. The judge doesn't buy it and recommends Sherlock be fired for that, among other things.
- Showed up from time to time on Law & Order. For example, sometimes they'd call Con-Ed and claim they smelled gas. Other times they'd just snow the super with "We have badges, it's cool."
- Law & Order: Special Victims Unit:
- In an episode, Benson and Stabler go to the suspect's apartment to question him and hear him having consensual sex with his girlfriend. They break down the door, and Stabler smirkingly claims that they had exigent circumstances because they heard a woman moaning.
- An odd example comes up when ADA Cabot orders Stabler and Benson to search a house for evidence in a child-molestation case, saying that she has a search warrant. It turns out that she lied. The evidence is still ruled admissible, as it wasn't the suspect's house that was searched, but the judge tears Cabot a new asshole over this.
- "Mr. Monk and the Very, Very Old Man" does this when Monk and Stottlemeyer show up at the house of George Rowe, following a lead in the death of Miles Holling. Stottlemeyer sees a messy room through the window, suggesting a fight. Monk briefly challenges Stottlemeyer on if they have enough probable cause to enter without a warrant, then they enter.
- "Mr. Monk Goes to a Wedding" lampshades it when Stottlemeyer uncovers evidence tying Jonathan's new wife to an attempt on Randy's life:
Natalie Teeger: You broke into her room? Is that legal?
Captain Leland Stottlemeyer: You don't need a search warrant to go into a hotel room if it's after checkout.
Adrian Monk: Is that true?
Captain Leland Stottlemeyer: I don't know.
- Played With in Witchblade in which a By-the-Book Cop visits the home of a man he knows to be a serial killer but has no evidence, trying to goad the man into revealing something, but goes away empty-handed. He later learns that there was a victim imprisoned inside the apartment, and if he had burst in on some flimsy excuse, he could have saved her life.
- In White Collar, Peter is a By-the-Book Cop, so he won't use this trope. That's why Neal frequently sets up the situation where Peter can still do this and yet avoid any problems. In one episode, the feds know that a certain guy is producing fake bearer bonds, but there's not enough evidence to get a warrant to raid his warehouse. So, Neal leaves the area he's supposed to stay in and breaks into the warehouse. The bad guy captures him and is smug about it until he realizes what happened. By law, the FBI is allowed to pursue a fleeing convict (Neal) to anywhere they know he is (thanks to his ankle monitor). If, in the process of pursuing him, they happen to find evidence of a crime, they're allowed to make the arrest, and the search is legal. Cue Peter and the other feds bursting into the warehouse and arresting everyone.
- Played straight on The X-Files episode "Home". Mulder and Scully go to a house in order to locate some suspects. They don't have local law enforcement with them, but as FBI Agents they have jurisdiction, so that's not an issue. Upon arriving at the house, the door is unlocked but it appears no-one is home. Mulder starts to open the door to go inside, but Scully stops him, correctly saying that "there's no probable cause" (that a felony has occurred or is occurring, which would allow them to enter the house without a warrant). Taking out his flashlight, Mulder shines it inside and they both see a bloodstained knife lying on the kitchen floor. Without saying a word, both of them draw their guns and enter the house, because now there is probable cause.
- Played with in an episode of Adam-12. Reed and Malloy serve an arrest warrant for a misdemeanor and Reed helpfully (he thinks) goes into the back of the house to make sure the back door is locked. The suspect tells him not to, however, and in the man's kitchen Reed stumbles on drug manufacturing supplies. This is ultimately ruled an illegal search even though Reed wasn't actively looking for evidence, and the drug charge is dismissed.
- The Mentalist flipflops between playing the trope straight and having Reality Ensue. On the one hand, Lisbon's team members sometimes break into houses while pretending to hear cries for help. On at least one occasion, however, Jane, a police consultant who in reality would be subject to the same rules as the police themselves, inadvertently leaves traces of his breaking-and-entering behind and blows their murder case against a contract killer until the team can find new evidence.
- Lampshaded in Heavy Rain when Blake blatantly kicks in a suspect's front door in order to search his apartment:
- Just about everyone in Criminal Case, including the player character, should be hauled before Internal Affairs for this. During an early Grimsborough case, a suspect refuses to let Jones and the PC search her apartment unless they can show her a warrant. Jones calls the request "cute". The apartment scene is searched without a warrant.