Question: What happens if you put your property in the hands of a private party, then that party calls the police and allows them to search it? Is the police search valid?
Answer: A property owner has, at best, a limited expectation of privacy in property she has temporarily ceded to a private business. Usually, if an employee of the business stumbles upon evidence of crime as it relates to the ceded property, the police will be justified in conducting a follow-up search without obtaining a warrant.
In this kind of situation, a key question is often whether, in conducting its own search, the police went beyond the scope of the original, private search.
Not all courts, however, approach follow-up police searches identically. For instance, some have applied this factor—whether the police went beyond the scope of the original search—differently than others when it comes to electronic data. (See Ramsay C. McCullough, "Circuits Split on Government Warrantless Search of Electronic Data," The National Law Review, June 17, 2015.)
Further, some state constitutions and laws provide more privacy protections to their citizens than the federal Constitution does. In those states, it’s possible that a court would find inadmissible evidence that another court would admit under the U.S. Constitution.
Example: Employees of a shipping company inspecting a damaged package discovered a white, powdery substance and called federal agents. The agents examined the damaged package; tests of the substance showed it to be cocaine. The search was legitimate because it didn’t interfere with a reasonable expectation of privacy. (U.S. v. Jacobsen, 466 U.S. 109 (1984).)
Example: A defendant gave his computer to a private business hired to repair it. The computer technician discovered child pornography pictures stored on the computer and called the police. The police viewed the obvious photographs in the same format as the technician, then enlarged them and viewed them as a slideshow. Even though the police enlarged the photographs, they didn’t see anything that the technician hadn’t already seen. The police search was essentially identical to the private search and the police learned nothing more than had been already been learned in the private search. The search was therefore valid. (U.S. v. Tosti, 733 F.3d 816 (9th Cir. 2013).)
For more on searches by people not employed by the government, see Searches by Private Citizens.