Stewart was a detective in Narcotics who worked with Detectives Joey Quinn and Yuki Amado during their time in Narcotics. At some point during their time together, Stewart developed a crystal meth problem and Joey figured it out. Rather than bust him for it, he tried to protect him from the fall he would take if anyone found out. Then one day during a bust, Stewart made a bad judgement call and shot an unarmed coke dealer. The dealer survived, but was left paralyzed. After this, Stewart went on a bender and eventually ended up committing suicide by eating his gun. As a result of the fallout, Joey was transferred to Homicide while Yuki transferred over to Internal Affairs to get Joey for not stopping Stewart sooner.