This shouldn't be any different than if a law enforcement official wanted to search your laptop or tablet. The same rules would apply. I know in states in the US where operating a cell phone while driving is enforced, if an accident occurs, the police can retrieve your cell phone records to determine whether you were using the phone at the time of the accident. Then you could face additional charges for this. Regardless, they still need a warrant to get these records.
International Level: Envoy / Political Participation: 241 24.1%
A unanimous Supreme Court ruling today gives a victory to privacy advocates by limiting police ability to search cell phones of criminal suspects upon arrest and without a warrant.
In a 9-0 decision, the justices said smartphones and other electronic devices were not in the same category as wallets, briefcases, and vehicles -- all currently subject to limited initial examination by law enforcement. Generally such searches are permitted if there is "Probable cause" A crime has been committed, ensuring an officer's safety, or preventing the destruction of evidence.
Criminal suspects in Massachusetts and California were separately convicted, in part, after phone numbers, text messages, photos and addresses obtained from personal electronic devices linked them to drug and gang activity.
The search cases gave the high court a timely opportunity to re-enter the public debate over the limits of Americans' privacy rights, with a focus on the ubiquitous cell phone and its vast storage of information and video. Ref. CNN
FBI gags state and local police on capabilities of cellphone spy gear:
The FBI requires state and local police to keep quiet about the capabilities of a controversial type of surveillance gear that allows law enforcement to eavesdrop on cellphone calls and track individual people based on the signals emitted by their mobile devices Ref. Source 7