Police officers are generally entitled to search people they arrest and the area immediately around them. So, if an officer slaps the cuffs on you, pats you down, and finds a cigarette pack in your pocket, he can see what’s in it. The question that courts struggled with—up until a June 2014 decision by the Supreme Court—is whether an officer who finds a cellphone on an arrestee can search that, too.
The Court issued a unanimous opinion holding that officers generally need warrants to search cellphones. The ruling means that officers can’t automatically examine the digital evidence on the mobile phones of their suspects.
To understand the Court’s rationale and the ins and outs of this area of law, see Cellphone Searches After Arrest.