In Riley v. California, the U.S. Supreme Court ruled that police conducting a lawful search incident to arrest must generally obtain a warrant before searching information stored on a cell phone. This ruling has the following implications. First, the notion that officer safety and the preservation of evidence are the reasons for allowing a warrantless search of the person of the arrestee, as well as a search of the scene of the arrest. Secondly, warrant requirements can protect privacy stored on a cell phone because of requirements that can narrow the scope of the search and the type of information that might be gathered. Thirdly, limitations on how long the government may retain information and the filtering agent（or devices which have a filtering algorithm）are useful.