Jester was a member of the Grand Army of the Republic as a clone trooper during the Clone Wars. Within his squad, he had a reputation for meticulously cleaning his DC-15 blaster rifle after each and every operation.
During the conflict known as the Battle of Christophsis, Captain Rex and Commander Cody detected an unusual signal frequency originating from Sergeant Slick's living quarters, leading them to believe that a Separatist spy had infiltrated the ranks of the platoon. As a result, Jester, along with the other troopers in his unit, were summoned back to the officers' quarters for individual questioning regarding their activities from earlier in the evening. Jester felt anxious about this, but another clone, "Sketch", corroborated Jester's routine of frequently cleaning his blaster. Jester then presented his spotless weapon to Cody as proof of his innocence, and he was dismissed as a suspect.
Slick was ultimately exposed as the traitor and fled the barracks. After escaping, he proceeded to sabotage the Republic's gunships, AT-TE walkers, and also the armory. When trooper "Gus" noticed Slick making his way toward the base's command center, Rex and Cody instructed Slick's squad to establish a secure perimeter. Subsequently, the two officers were successful in apprehending Slick.