As I discussed in my last post, the U.S. Department of Justice recently published a new policy that generally requires federal law enforcement agencies to obtain a search warrant before using a cell-site simulator device, otherwise known as a stingray. But the policy itself does not create grounds for someone to bring a lawsuit for improper use of a cell-site simulator. People will have to look to the courts, and to the protections against unreasonable search and seizure offered by the Fourth Amendment and by individual state constitutions. While warrantless use of cell-site simulators likely violates the Fourth Amendment, it may be that even warrant-based searches inherently violate our constitutional Fourth Amendment right against unlawful searches because such warrants are, necessarily, general warrants that have long been prohibited.
The Fourth Amendment protects people from unreasonable searches and seizures. Typically, a person’s body, home, and belongings cannot be searched unless the government has first obtained a warrant from the court. The warrant has to be supported by probable cause—in other words, a particular and reasonable basis for believing that a crime was committed, and that a search will turn up evidence of that crime. Of course, Fourth Amendment protections are more complicated than that. For one thing, a person can be subject to a brief seizure and search if a law enforcement officer has “reasonable suspicion” that the person has or is about to commit a crime, or that the person has a weapon on them or in their vehicle. For another thing, law enforcement can use the “exigent circumstances” exception to conduct a search without a warrant, when they think they will not have time to get one. In practice, these exceptions can be abused, sometimes systematically and discriminatorily, by law enforcement (my colleague has discussed this here; the report on stop and frisk practices in Massachusetts, published by ACLU Massachusetts, provides additional insight into the issue). But the Fourth Amendment—and similar rights afforded by state constitutions—continues to be a valuable protection against unreasonable searches and seizures.