[1] From 1987 to 1994, Cleary served as an Assistant U.S. Attorney for the Southern District of New York, eventually becoming Chief of the Major Crimes Unit.
[1][2] In 1996, Cleary was appointed lead prosecutor in the Unabomber case, United States v. Theodore J. Kaczynski.
Later in 2002, he was appointed as Acting United States Attorney for the Southern District of Illinois while nominee Miriam Miquelon awaited confirmation.
[2] In February 2006, in the wake of a police investigation codenamed Operation Slapshot, National Hockey League commissioner Gary Bettman announced that the NHL had retained Cleary to conduct its own investigation into the involvement of Rick Tocchet, an assistant coach for the Phoenix Coyotes, in an illegal bookmaking ring.
[5] In January 2024, Cleary joined the New York City law firm Patterson Belknap Webb & Tyler as Of counsel.