A cellphone seized during an arrest can be a prosecutor’s dream and a defense attorney’s nightmare. It can reveal not just whom the owner has called, but also his or her whereabouts, bank records and more.

Jurisdictions are deeply divided on whether and to what extent police can search, without warrants, the phones they find on people they arrest. Two petitions filed this summer are asking the U.S. Supreme Court to weigh in. The justices have not yet scheduled the petitions for consideration at conference.

In United States v. Wurie, the government argues that the police did not violate the Fourth Amendment when they searched the call log on Brima Wurie’s cell phone after arresting him in Boston. In Riley v. California, defense attorneys say that David Riley was the victim of an unconstitutional search after police used video and pictures from his phone as evidence.

“It’s an issue that affects police operations on a day-to-day basis and privacy at the most fundamental level,” said Jeffrey Fisher, counsel of record in Riley and director of the Supreme Court Litigation Clinic at Stanford Law School.

The cases have key differences. Wurie did not have a smartphone. After witnessing him allegedly deal drugs, officers opened his “flip phone” and saw that he had many missed calls from a number labeled “my house.” Police later found the address, got a search warrant, and seized money, drugs and a gun there.

The U.S. Court of Appeals for the First Circuit vacated Wurie’s convictions on two counts in May, reasoning that the items obtained at the home were the fruit of an illegal search. (The court in July declined to revisit the panel ruling; the chief judge wrote then that she hopes the Supreme Court will consider the case.)

In the California case, officers seized Riley’s Samsung smartphone as well as guns found in his car after stopping him in San Diego for driving with expired tags.

A cop scrolled through the phone at the scene and found words spelled in a way that indicated gang membership. At the station, officers looked through the phone a second time. There, they discovered photos and videos that seemed gang-related as well as a picture of Riley in front of a car that police suspected was involved in a shooting. Riley was later found guilty of shooting at an occupied vehicle, and got an enhanced sentence for involvement in a gang-related crime.

The Supreme Court has declined to hear this issue before, but the pending petitions argue that, given how common cell phones are, it is time to resolve the circuit split. If the high court accepts just one case, some criminal procedure scholars point to Riley as the better option because most cell phone users have smartphones now.

The legal underpinnings of this debate come from the court’s 1973 ruling in United States v. Robinson. There, the Supreme Court held that police do not need a warrant to search items—including closed containers—that they find on a lawfully arrested person.

Adam Gershowitz, a William & Mary Law School professor who has written about cell phone searches, said the Robinson Court could not have contemplated the potential evidence that today’s smartphones can contain.

“The amount of information that’s accessible if we take this doctrine to its logical conclusion is almost unimaginable, and it’s just going to get wider and wider and wider,” Gershowitz said.

Under Robinson, police have perused pocket diaries and address books that they seize after an arrest. The government in Wurie argues that cellphones are no different.

“It would be anomalous to provide arrestees who use more sophisticated technology a special protection from police investigation that does not apply to those who keep records of their criminal activity with only pen and paper,” Justice Department lawyers wrote in their petition, filed in August.

The government also argues that searches like the one that Wurie faced are valid because police need clear rules when making on-the-spot decisions; arrested people have diminished expectations of privacy; and cell phone contents can be destroyed remotely.

Fisher, though, says that two key justifications for the search-incident-to-arrest doctrine—officer safety and fears about destruction of evidence—do not apply. Police can ensure that no one ruins a phone’s contents by turning it off or putting it in a signal-blocking bag, he wrote.

Instead, Fisher argues, the warrantless searches are unreasonable because of the “profound privacy concerns” they raise. A cellphone is not a closed container a la Robinson, he wrote, but a “mini, yet powerful, computer that happens to include a phone.”

Jamie Schuman is a freelance writer and graduate of The George Washington University Law School.