Let me start by stating I may be biased on this one. Recently a friend’s daughter was nearly killed by someone who ran a red light and hit her and a friend, then fled the scene on foot, leaving behind the car and his cell phone still logged into Facebook. Having said that: The rules governing the use of such devices need to be clearly established and either a warrant or exigent circumstances need to exist. Since the vehicle was used and crashed, the driver(s) can be appropriately searched, similar to the way a driver would have a breathalyzer done if the police suspect DWI. If there’s reason to believe the driver was on their phone (such as witnesses testifying) or the crash is serious in nature (people being taken to the hospital, vehicles totaled, etc) that should be enough for exigent circumstances. At a minimum it should be enough to take the phone into evidence until a warrant can be issued.