If law enforcement were to seize your cell phone, laptop or tablet they would likely obtain a search warrant to further search that device for any evidence of criminal activity.
As these devices are essentially mini-computers there is much information on there that could be used as evidence against a person depending on the nature of the charges. Things like GPS history, text messages, e-mails, browser history and photographs are all things that law enforcement will be looking to recover from the phone in order to try to support the charges filed against a particular person.
A specialist within the law enforcement would conduct what is called a forensic search of the phone in an effort to try to uncover this evidence.
