Patrick Bonanno is a lieutenant with the Massachusetts State Police, Organized Crime Division. When the Leverage team needs to put the cuffs on a mark, they call Bonanno due to the fact that they realize he is an incorruptible cop.
About a year after the Leverage team reassembled in Boston, Lt. Bonanno was shot and hospitalized due to a case he was working on, involving shady mayor Brad Culpepper III. Nathan Ford took it upon himself to help Lt. Bonanno with his case.
Lt. Bonanno's wife informed Nate that her husband had figured out that he was the one "helping out" on some of his cases, and that he wanted to buy Nate a drink ... and then arrest him.
Bonanno does eventually recover from his gunshot wound, but is shown walking with a cane in the Season 3 episode The Jailhouse Job. Also, sometime after he recovers, he is promoted to Detective Captain.
In the Season 4 episode The Boys Night Out Job, he is revealed to be on friendly terms with Nate and his crew - and is even willing to help them out. It is also implied in this episode that Nate and the team rely on Bonanno a lot with their cases.
- Even though Lt. Bonanno was only shown being "used" to help the Leverage team twice ("The Beantown Bailout Job" and "The Ice Man Job"), it was implied in "The Three Strikes Job" that he was involved with more than just two jobs.