An arrest actually occurs when a police officer indicates by word or action an intention to take a person into custody. Except under certain circumstances, police are required to have a valid warrant before making an arrest. One way to obtain a warrant is when a victim or witness goes directly to the county state's attorney's office with information about a crime, signs a complaint against the person who has allegedly committed the crime, and appears before a judge who issues an arrest warrant for the alleged offender. Another way is when a police officer files the complaint and goes before a judge to seek a warrant.
A police officer may make an arrest without a warrant if the officer witnesses a crime being committed. Police may also make an arrest without a warrant if there is probable cause that an officer occurred and that the person who would be taken into custody committed the crime. Unless it is an emergency, however, a police officer cannot enter a person's home without a warrant to make an arrest. When a person is arrested, he or she is not necessarily charged with a crime. Some people who are arrested are taken into custody, questioned, possibly put into a lineup, and then released without being charged with an offense.