|Portrayed by||Wilmer Calderon|
Marvin Osminkowski, known as "Oz" professionally, was a notorious drug dealer with a reputation for catering to the children of the rich.
He had a reputation for living off the grid that made it hard for the police to ever track him down, word about the clubs that he would visit being passed around by word-of-mouth rather than anything more formal.
Oz ran into trouble when he attempted to force Nicole Hixton, daughter of the lottery winner Jay Hixton, to return to her old drug habit after her parents helped her go clean, prompting her father to call his old friends, Ty and Greg Page, to confront Oz about his actions towards Nicole. Oz subsequently firebombed the Page brothers' care to teach them a lesson.
Suspecting that Oz was involved in Hixton's murder, Castle and Beckett went undercover to the club where Oz was 'working' that night, Kate tricking Oz into revealing that he had drugs on him and allowing her to arrest him on charges of possession with the intent to sell.
However, although Oz would serve time for the drugs, contributing to the delinquency of a minor and attempted murder, he was able to provide an alibi for the time when Hixton had been killed.