Long Shadows by David Baldacci

LONG SHADOWS is an overall entertaining procedural that follows an FBI agent and an FBI contractor as they travel to Florida to investigate the brutal killing of a federal judge and her bodyguard. Decker is a contractor with an excellent record, who is not particularly well-liked by the bureau. He has an eidetic memory as well as a bit of synesthesia from a head injury when playing football when he was younger, and it has made him an excellent detective. He has been assigned to work with Freddie White, a Black agent, who has been blocked from promotions for too long. While they are forced into the partnership, they do find themselves working well together as they proceed on the case.

The case itself ends up getting quite twisty with other crimes following the initial ones, leading them down paths that were long in the past and through politicians and blackmailers to the explosive end. There were plenty of red herrings along the way, as it seems that everyone had a bit of motive in this case.