The criminal justice process usually begins when a police officer arrests a person. The key to an arrest is the exercise of police authority over a person, and that person's voluntary or involuntary submission. A police officer may usually arrest a person in the following circumstances:
The Police Officer Observes a Crime: If a police officer personally sees someone commit a crime, the officer may arrest that individual.
The Police Officer Has "Probable Cause" to Arrest: When a police officer has a reasonable belief, based on facts and circumstances, that a person has committed or is about to commit a crime, the officer may arrest that person. This is known as "probable cause," and may arise from any number of different facts and circumstances.
An Arrest Warrant Has Been Issued: When a police officer has obtained a valid warrant to arrest a person, the arrest is lawful. An arrest warrant is a legal document issued by a judge or magistrate, usually after a police officer has submitted a sworn statement that sets out the basis for the arrest. When issued, an arrest warrant typically:
- Identifies the crime or crimes committed
- Identifies the individual suspected of committing the crime
- Specifies the location where the individual may be found
- Gives a police officer permission to arrest the person identified in the warrant.
Challenging An Unlawful Arrest
During all stages of the criminal process, including the arrest, police officers must protect citizens' constitutional rights, including the right to remain silent and the right to be free from unreasonable searches. In the event that these rights are violated, a court may deem the arrest unlawful and order the case against the arrestee dismissed, or certain evidence may be thrown out of the case. While a criminal suspect may question the lawfulness of an arrest when it is happening, including the basis for the arrest and the actions of the police officers, that battle is best fought in court rather than on the street.