MEMPHIS, Tenn. -- For many, it's their lifeline, an extension of themselves.
Cellphones are little devices that can tell a lot about you.
"Some people, their cellphone is like their whole life because they don't have home phones. That's their whole life. They keep so much," Edie Parker of East Memphis said.
It's why cellphones have become key evidence police use in their investigations.
Now the Supreme Court is weighing in on how officers get that information.
They are taking up two cases dealing with whether police need a search warrant to go through the cellphones of people they arrest.
Prominent Memphis Defense Attorney Leslie Ballin says with how phones are used these days, a warrant should be required.
"I think that there is sensitive information that people should have an expectation of privacy in. This is an extension of their private lives this phone," Ballin said.
Memphis Police declined to talk with us about their use of cellphone evidence, but did send us a statement saying their department has solved many crimes through vital evidence obtained from cellular phones.
Think about it. Almost every person owns a cellphone, and if you're ever arrested and that phone is on you, it can become evidence.
It can tell police who you called and who is in your contacts. With GPS tracking, it can show where you've been, and even store calendars, photos, and financial information.
Those things, if used in a court of law, could be used against you.
Assistant District Attorney for Special Prosecution, Reggie Henderson, says cellphone evidence is crucial in a lot of his cases, including the high-profile Taylor Bradford Murder Case. Bradford, a University of Memphis football player, was shot and killed in an orchestrated on-campus robbery.
The mastermind of the crime was never at the scene and claimed he knew nothing about it, but his phone proved otherwise.
"When we were able to look into the cellphone and all of that, we found just prior to the robbery and immediately following the robbery, in the span of about 45 minutes or so, this individual had talked to the people committing the robbery about 18 times," Henderson said.
It made a connection between the criminals and helped in landing a conviction.
Henderson says legal questions can be avoided by police going ahead and getting warrants before ever looking at a cellphone, something he says Memphis police do in its cases.
"The bottom line is it's just another tool, another piece of information I think is very important that is being used extensively. That is part of the process now when crimes are being investigated," Henderson said.
Also at question is whether cellphones need to be searched immediately or can police wait until the warrant is issued.
Those pushing for immediacy say any delays could allow critical evidence to be remotely erased from a phone. Others say with something like an abduction or missing persons case, there should be as exception.
The Tennessee Legislature recently passed a bill by Senator Mae Beavers of Nashville that would require police to get a warrant before they tracked your cellphone calls.
The bill passed both chambers and is awaiting Governor Bill Haslam's signature.