Adam Kirk was a police officer with the San Francisco Police Department for over twenty years.
Kirk was a longtime partner with Leland Stottlemeyer, prior to the latter's promotion to captain. Kirk suffered from a volatile temper, and over the course of his career, faced numerous accusations of police brutality and excessive force. On at least one of these occasions, Adrian Monk (at the time still on the police force) testified against him.
Around 2001, Kirk arrested Leonard Stokes on murder charges, obtaining a confession from Stokes in the back of his police car. Stokes soon recanted, however, and accused Kirk of beating the confession out of him. Roughly 14 months later, Kirk received a call from a low-level criminal named John Gitomer, offering him details about an upcoming drug shipment. By this time, Kirk was having problems with alcohol and was estranged from his wife, Anita. Nevertheless, he went to the carnival and met with Gitomer alone, who insisted on riding the Ferris wheel before divulging any information. Once they were on the ride, Gitomer started shouting that Kirk was beating him. The ride stopped and Kirk immediately stepped off the ride. A few seconds later, the Ferris wheel operator screamed and Kirk turned around to see Gitomer double over with a knife in his chest.
Kirk was immediately suspended from duty and indicted for murder. He swore that he never touched the teen, let alone stabbed him, and Stottlemeyer, who trusted his old partner, asked Monk to help clear him. Though Monk was all too familiar with Kirk's violent history, he agreed to take the case.
Monk eventually discovered that Stokes had framed Kirk for the murder, in order to get his confession thrown out before his trial. Stokes was arrested at the carnival shortly after murdering his lover and accomplice, the wheel operator. Kirk was exonerated, and reinstated, and made sure to thank Monk after being reinstated.