The police are often allowed to trick you. They're free, for instance, to hide behind freeway overpasses or shrubs while unsuspecting motorists barrel down the road. They may also go undercover.
At the same time, the police are generally allowed to search your home or your stuff if you agree, even if they don't have probable cause or a warrant. (They're sometimes allowed to search even if they've gotten consent without being completely forthcoming.)
So what happens when someone lets the cops peek inside a home or have a look around only because the officers are pretending not to be cops? Is the search legal?
The answer depends on factors like the extent of the search and the degree of the officers' deception.
If police officers get into a house by deceiving an occupant into believing they're something other than police officers, evidence they find inside might be inadmissible in court. (More on that below.) But many courts—even if not all—have said it's fine for the police to play pretend in order to get you to simply open the front door and talk to them. Consider the following example.
Police officers in Colorado receive an anonymous tip that people are selling drugs out of an apartment. Officers Carver and Hauk go to the apartment to conduct a "knock and talk" with the occupants. Carver stands out of view while Hauk knocks on the front door. After a minute and no answer, Hauk knocks again. Someone inside asks (through the closed door), "Who is it?" Hauk responds, "Maintenance."
Preston, who lives in the apartment, opens the door. When he does, Officer Carver steps into view and joins Officer Hauk. The officers can see another man, Wallace, inside the apartment, behind Preston. Officer Carver sees a glass pipe on a table inside the apartment. Wallace runs toward the back of the apartment. Carver, who assumes Wallace is either fleeing, destroying evidence, or trying to get a weapon, enters the apartment to pursue.
Officer Hauk pulls Preston to the ground in the doorway to keep him from interfering. When Carver catches up to Wallace out behind the apartment, Wallace drops a knife. Carver finds cocaine in Wallace's pockets.
Before his trial for several drug-related offenses, Preston moves to suppress the evidence found inside the apartment. He argues that the police unlawfully pretended to be maintenance workers and that their deceit led to the entire episode.
The appeals court considering the case explains that there's a difference between using deceit only to get an occupant to open the door and using it to gain consent to enter the residence. The court observes that the officers used their ruse only to get someone to open the door—not to get someone to allow them inside. The court denies Preston's motion to suppress. (People v. Nelson, 296 P.3d 177 (Colo. App. 2012).)
Even though entering a house is a greater privacy invasion than getting an occupant to merely open the door, some courts have found it legal for police to go into a home under false pretenses. In other cases, courts have held that officer trickery went too far.
The U.S. Supreme Court, for instance, once sided with law enforcement in a classic case of undercover tactics. The defendant had invited an undercover agent to his home for a drug sale. His only concern was whether the agent was a willing and able buyer. During two visits to the defendant's home, the agent never saw, heard, or took anything that the defendant didn't consider. The Court held that the agent's misrepresentation of his identity didn't violate the defendant's Fourth Amendment rights. It held that the drugs the undercover officer purchased were admissible at trial. (Lewis v. United States, 385 U.S. 206 (1966).)
Cases can go the other way, though. For example, in a 1986 Ohio case, two officers visited a fraternity house in order to follow up on complaints about illegal alcohol sales there. One of the officers lied to the fraternity house manager that he was an alum of the house. He said he wanted to take a look on behalf of his brother, who was considering attending the school and joining the house. The manager showed the officers around. One officer saw a soda machine that dispensed beer cans and bought one. Before leaving and getting a search warrant, one of the duo gave the manager a fake name and address.
The state supreme court held that the house manager's invitation to enter wasn't "free and voluntary" consent, and that the officers unlawfully entered the house. The court noted that the home wasn't a "commercial center of criminal activity," and that the invitation to enter wasn't "for the purpose of conducting illegal activities." (State v. Pi Kappa Alpha Fraternity, 23 Ohio St. 3d 141 (1986).)
If you want to understand how the law in your jurisdiction applies to your situation, consult an experienced criminal law attorney. A knowledgeable lawyer will be suited to assessing the precise circumstances of a case.