Locating someone in the penal system can be intimidating. However, an arrest number can make the task relatively easy. An arrest number is kept on record at the precinct where the person was arrested. It tells the law enforcement officer the arrested individual's name, the crime he was accused of and where the he is currently located. Although an arrest number isn't useful in locating a person once he is released from prison, there are several ways to use an arrest number to find a person still in the penal system.
Search online for the website of the penal system where the person was arrested. Some websites allow inmate searches. Search by arrest number to find in which prison in any system the person is located.
Contact the arraignment clerk or another official at the courthouse where the person was arrested. Provide the arrest number to receive the person's location.
Call the police station in the district where the arrest took place. Explain why you need to find the person. Be prepared to explain your relationship to the person and your reason for contacting him.
Contact a private investigator. She may have greater access to police officials and databases than you do --- and will be able to continue helping you locate the person if the arrest number leads you to a dead end.