Good Junk (Cliff St. James) by Ed Kovacs

Cliff St. James is back in action in post-Kathrina New Orleans and carrying a ton of guilt caused by the death of a sparring partner during a MMA fight. A good murder investigation is just the thing to pull him out of depression and his old friend Honey Baybee offers him just that. The murder victims are two gay lovers, employees of NASA’s nearby Michoud facility.
Cliff is one tough dude, all guns, knives, gadgets and martial arts. Enlisted as a special consultant to the cops Cliff is endangered several times by his new reluctance to use deadly force. Aside from that he's still struggling with his feelings for Honey.
The investigation draws in a lot of suspects and other people interested in the outcome, from spies to the FBI. In fact, this is more of a David Baldacci style thriller than your average PI novel. It is that direction that will make this book a good read for fans of Lee Child and Baldacci but might dissapoint fans of the more classic stuff.
I do think his consultant-role is a good way to make a detective be able to investigate a murder but still remain a bit of a lone wolf. Not sure how realistic it is the NOPD would contract someon like Cliff, though.