Police officers are allowed to use deception to investigate crime. (See Is police deception always legal?) They often use at least some degree of deception in order to convince someone to agree to a search. That’s because, with proper consent, officers don’t need probable cause or a warrant. But, if the suspect’s consent is null and the officers don’t have another basis for the search, the resulting evidence will be inadmissible in court. (See What is a motion to suppress?)
The rules may vary slightly from one court to another. But usually, if officers simply fail to tell a suspect that an inspection may lead to criminal charges, consent will be valid. On the other hand, consent may be invalid when officers mislead a suspect about who or what they’re investigating.
Federal agents had an indication that Davis might have an illegal firearm. They went to his house; Davis, who had a prior felony conviction, understood that the agents were there to look for a machine gun. He told the agents that he had other guns. He let the officers into the house and showed them several firearms. None was a machine gun. He was later charged with unlawful firearm possession by a convicted felon.
A federal appeals court held that Davis’s consent was valid. It observed, “The mere failure of the officers to give an encyclopedic catalogue of everything they might be interested in does not alone render the consent to search involuntary.” The court also noted that there was no indication that the officers set out with a motive other than to find the machine gun they suspected Davis had. According to the court, that weapon, rather than Davis's potential illegal possession of other guns, was their motivation. And they didn’t indicate to him that nothing other than a machine gun could lead to prosecution. The guns were therefore admissible evidence. (United States v. Davis, 749 F.2d 292 (5th Cir. 1985).)
An agent with the Bureau of Alcohol, Tobacco, Firearms, and Explosives (“ATF”) began investigating Harrison. Harrison reportedly owed money to a suspected firearm trafficker and was selling drugs out of his apartment. The agent surveilled Harrison’s apartment for several months, but didn’t see anything that would establish probable cause for a warrant. So, the agent and a colleague knocked on Harrison’s door and reported that they were there because they had received an anonymous tip that there were drugs and bombs in the apartment. The agents explained that it was matter of community safety. The primary agent asked if he and his colleague could come in and have a look around. He said, “We're not here to bust you on a bag of weed. ... We have bigger fish to fry than a small bag of weed.” Harrison, who had a prior felony, gave the agents permission to search the apartment. During the search, they found a loaded handgun in a hole underneath a sink.
A federal appeals court upheld a lower court’s finding that the search was illegal. The appeals court explained that “deception and trickery” are factors that can make consent “involuntary.” Another factor, the court explained, is whether officers tell a defendant that he or she has a right to refuse consent to a search. (Officers generally aren’t required to advise defendants of the right to refuse, though.) The court ultimately held that Harrison could have reasonably believed he and others were in danger because of a bomb. How could he say “no” to that? His “consent” was therefore involuntary. (United States v. Harrison, 639 F.3d 1273 (10th Cir. 2011).)