The next time you’re in California, you might not want to bring your cell phone with you. The California Supreme Court ruled Monday that police can search the cell phone of a person who’s been arrested — including text messages — without obtaining a warrant, and use that data as evidence.

The ruling opens up disturbing possibilities, such as broad, warrantless searches of e-mails, documents and contacts on smart phones, tablet computers, and perhaps even laptop computers, according to legal expert Mark Rasch.

The ruling handed down by California’s top court involves the 2007 arrest of Gregory Diaz, who purchased drugs from a police informant. Investigators later looked through Diaz’s phone and found text messages that implicated him in a drug deal. Diaz appealed his conviction, saying the evidence was gathered in violation of the Fourth Amendment, which prohibits unreasonable searches and seizures. The court disagreed, comparing Diaz cell phone to personal effects like clothing, which can be searched by arresting officers.

“The cell phone was an item (of personal property) on (Diaz’s) person at the time of his arrest and during the administrative processing at the police station,” the justices wrote. “Because the cell phone was immediately associated with defendant’s person, (police were) entitled to inspect its contents without a warrant.” 

In fact, the ruling goes further, saying essentially that the Diaz case didn’t involve an exception — such as a need to search the phone to stop a “crime in progress.” In other words, this case was not an exception, but rather the rule.

Rasch, former head of the Justice Department’s computer crime unit, pulled no punches in his reaction to the ruling.

“This ruling isn’t just wrong, it’s dangerous,” said Rasch, now director of cybersecurity and privacy at computer security firm CSC in Virginia.  “It’s remarkable, because it simply misunderstands the nature of these devices.”

The door is open for police to search the entire contents of iPhones or other smart phones that people routinely carry, he said.

“In fact, I would be shocked if police weren’t getting instructions right now to do just that,” he said.

By applying the “personal property on the defendant’s person” standard, Rasch said, the ruling could logically extend to tablets or even laptop computers, he said.

It also flies in the face of established law, which prohibits the warrantless search of briefcases by police, other than a quick search for weapons, Rasch said.

In its ruling, the majority likened cell phone inspection to police inspection of a cigarette pack taken from a suspect, which was ruled a legal search in a prior case.  A second ruling was cited involving the search of clothing removed from a suspect.

Rasch said the analogies don’t hold, however, as modern phones that can store years’ worth of personal information are a far cry from drugs hidden in a cigarette case or clothes pockets.

“There is a process for looking at data inside devices,” he said. “It’s called a warrant.”

(Read More: MSNBC)