Showing Bloodlines (Boystown #7) by Marshall Thornton

In the seventh book of the award-winning Boystown Mystery series, Private Investigator Nick Nowak finds himself simultaneously working two cases for his new client, law firm Cooke, Babcock and Lackerby. A suburban dentist has been convicted of murdering her adulterous husband. Nick is asked to interview witnesses for the penalty phase of the trial--and possibly find the dead man's mistress. At the same time, he's deeply involved in protecting Outfit underboss Jimmy English from a task force out to prosecute him for a crime he may not have committed. While juggling these cases Nick slowly begins to rebuild his personal life.

Winner Lambda Award, Gay Mystery 2015