If the police want to go through your car, backpack or wallet looking for evidence, they can - if they have reason to suspect you're concealing traces of a crime. But according to the U.S. Supreme Court, a cell phone is different. Law enforcement officials need a warrant to search your cell phone, the justices decided in 2014.
A warrant is an official document that has been reviewed and approved, and when signed allows a process to continue. Warrants are used by many branches of government to establish procedural standards that will stand up to scrutiny if the case goes to court.
In policing, warrants are a necessary step in establishing the authority to pursue a course of action such as a criminal complaint. For instance, a warrant to search a residence or business for evidence must be obtained by a law enforcement official because individuals are protected by the Constitution (Article 4) from unlawful search and seizure. Similarly, a person not arrested at the scene of a crime may be arrested by warrant after a judge has reviewed and approved the police evidence showing probable cause - that is, linking the person to the crime.
However, warrants - even 300 years into their use - are still a hotbed of law enforcement and judicial controversy because they are constantly being challenged and exceptions sought for "emergency" search and seizures. The war on drugs created the "no knock" search and seizure process that, with the approval of a judge's signature on a warrant, has been criticized across the country for harming innocent people, damaging property unnecessarily and leading to many police errors including ransacking the wrong property.
History of warrants
The use of warrants is directly derived from Colonial England, where such documents were signed by an officer of the Crown or the monarch himself. Warrants that weren't acted upon before the death of the King or Queen were null and void. Historians say that several peoples' lives were spared when in the 1500s they were about to be burned at the stake and word came that the Queen had died so they were released instead.
An early example of a fugitive from justice who was wanted by warrant was the fabled Robin Hood of Sherwood Forest in England whose fame and notoriety grew as the Sheriff of Nottingham searched for him. He was accused, we all know, of taking from the rich and giving to the poor. We can't corroborate his dalliance with Maid Marion.
Others who have outstanding arrest warrants include the artist Shepard Fairey, whose "Hope" poster was adopted by two-term American president Barack Obama during his initial campaign and whose signature image is of Andre the Giant, a wrestler, with the word Obey. Fairey was named in a warrant by Detroit police for tagging buildings with unauthorized artwork (called vandalism or graffiti because it was unauthorized) after completing a large mural and other installations for the city. If he is taken into custody on the warrant in the future, he may face a maximum 5-year jail term and up to $10,000 in fines.