Legally, arrest means exactly what I outlined earlier. Custody is the action a police officer actually performs when he takes a person to the police station and books them, ie, "the officer took the suspect into custody" - which means the officer has now taken responsibility for the person and their possessions and is required to keep an accounting of all such matters to satisfy the court.
Originally Posted by lxdude
Unfortunately, for the average person, arrest is confused with custody due to too many cop shows. :-)