The United States Supreme Court recently in Riley v. California ruled that law enforcement needs a warrant to search a person's cell phone. Mr. Riley was arrested on the highway. Taken back to the station, a detective looked at the contents of his cell phone resulting in further charges against Mr. Riley. The Court held the a warrant was required; that a significant amount of personal information is located on a person's cell phone; and, that an expectation of privacy exists with regard to cell phones. The Court is correct in its decision and the rationale for it. I would suggest that for many, the phone is the sole repository of personal information a person may possess.
In most warrants relating to drug investigations, the request includes cell phones on the premises or on the person the subject of the warrant. The rationale is that if you are selling or buying drugs the arrangements are being made through the phone. This would be a fairly reasonable inference to make. Too bad no one has land lines any longer where local calls can't be traced. Phone numbers, text messages, and other forms of messaging can be retrieved. One thing leads to another, once they find something of interest on your phone, they can obtain warrants for your on line services such as Facebook, twitter, etc.