It's easy for law enforcement to overreach their powers in their efforts to stop crime. As the police use ever-more-intrusive methods for tracking people, they often raise the argument that the innocent people caught up in their dragnets have nothing to fear.
At the border and in international airports, ICE and the Customs and Border Protection service have been routinely rifling through people's computers and smart phones. Away from the border, law enforcement needs a warrant before it can search your phone or another electronic device. So why have border agents assumed they didn't need one?
The mere fact that someone is under suspicion for a crime is not enough to justify a warrant for that person's cellphone. The mere fact that most people have a cellphone is not enough to justify a warrant. A warrant issued with no more specific reason than those is unconstitutional, the influential D.C. Circuit Court of Appeals ruled recently.
A homicide charge against a person is one of the most severe in criminal law. To be arrested for homicide, or any other criminal charge, the police must have probable cause, a legal requirement of sufficient reason from the facts and circumstances of the situation, that an individual has committed the crime. In general, the police must have probable cause to obtain a search warrant before searching for evidence.