(NBC News) — Police have a powerful tool in their fight against crime, the same tool you use to text your friends and plan your week: Your phone.
Now in two cases before the U.S. Supreme Court, the issue is whether police can look through that phone if you're arrested.
200 million Americans have smart phones crammed full of private information and images.
One modern smartphone can store ten times more information than that in all the libraries of the founding fathers, who banned unreasonable search and seizure in the Bill of Rights.
"There's really no end to the doorway law enforcement would have once it got access to your smart phone," notes technology security analyst Bob Sullivan.
Obama Solicitor General Michael Dreeben argued that's okay, claiming when you're arrested your expectation of privacy is reduced.
Stanford Law School Professor Jeffery Fisher argued the other side.
"An occasion of an arrest should not expose someone's entire life and their most private correspondence and letters to police investigation," he says. "Not just at the scene, but to be downloaded later at the police station and kept in perpetuity."
Justices seemed to agree.
Phone warrants are the middle ground. They allow police to seize a phone, but not look into it until a judge agrees that its contents might reveal a crime.