Your locker in the police station's locker room contains several of the items and equipment you'll need to do your job, and you'll be delving into it several times throughout the game. The locker combination (originally hidden in the Police Quest 1 VGA manual) is 2-6-9.
Since this IS a police simulation, you'll have to book offenders on various charges when it comes time to throw 'em in the slammer. The jailer will present you with a numeric keypad for this purpose. Using the following list of violations, look up ALL charges that apply to the perp in question, and enter them one-at-a-time into the keypad (make sure you press the ENTER button to confirm each code).
VIOLATION CODES
12509 - Possession Of A Concealed Weapon
12755 - Possession Of Cocaine
12876 - Possession Of A Controlled Substance
13301 - Failure To Stop For A Stop Sign
19221 - Stolen Vehicle
21068 - Evading Arrest
21490 - Failure To Stop For A Red Light
21603 - Driving Under The Influence Of Intoxicants
26504 - Exceeding The Maximum Speed Limit
29211 - Reckless Driving
44729 - Not In Full Control Of Faculties