Lieutenant Prosser was a Junior Officer in the UNSC Navy. In 2531, he assaulted a woman in a bar, in which Sergeant John Forge stopped and confronted the Lieutenant. They engaged in a fist fight, with charges brought upon Sergeant Forge.
Luckily for Forge, the woman proclaimed him as a hero and all charges were dropped, where he was later reassigned to the UNSC Spirit of Fire by Admiral Preston J. Cole personally. Lieutenant Prosser's status is unclear, though it is assumed that he was brought up on criminal charges.