The California Supreme Court ruled Monday that police can search text messages on the cell phones of people they arrest without obtaining a search warrant. Citing US Supreme Court precedent from the 1970s, the court held that reviewing cell phone text messages was a valid search incidental to arrest.

The ruling came in California v. Diaz, in which Ventura County resident Gregory Diaz was arrested for selling Ecstasy to an undercover informant. Sheriff's deputies seized Diaz' cell phone along with six tabs of the drug. An hour and a half after the arrest, a detective without a search warrant looked at the phone' text message folders and found a coded message referring to Ecstasy sales.

When faced with the incriminating text message, Diaz admitted to doing the drug deal. He pleaded guilty to transporting a controlled substance, but reserved his right to appeal. He was sentenced to probation and did appeal the lawfulness of the cell phone search.

In a 5-2 decision, the state high court majority held that the search was allowable under US Supreme Court rulings that permitted the warrantless searches of personal property "immediately associated" with the arrested person, such as clothing or cigarette packs. Writing for the majority, Justice Ming Chin held that the cell phone was personal property, that it was immediately associated with Diaz, and that the search was therefore valid.

But in a dissenting opinion, Justice Kathryn Werdegar argued that searching the cell phone's text messages was "highly intrusive" and could have been carried out after police obtained a search warrant. Earlier US Supreme Court rulings should be reevaluated in light of technological innovations, she wrote.

Justice Werdegar may have been in the minority in the California case, but the high court in at least one other state has ruled that warrantless searches of cell phones incident to arrest are unconstitutional. In Ohio v. Smith, decided in December 2009, the Ohio Supreme Court held that the warrantless search of a drug suspect's cell phone violated his Fourth Amendment protections against unreasonable searches and seizures.

"Once the cell phone is in police custody, the state has satisfied its immediate interest in collecting and preserving evidence and can take preventive steps to ensure that the data found on the phone is neither lost nor erased," Justice Judith Ann Lanzinger wrote for the majority in that case. "But because a person has a high expectation of privacy in a cell phone's contents, police must then obtain a warrant before intruding into the phone's contents."

With state supreme courts in two different states coming to starkly different conclusions about the constitutionality of warrantless cell phone searches incident to arrest, this issue would appear to be likely to be headed for resolution at the US Supreme Court.