Scott Speedman, who you may know as Dr. Nick Marsh from Grey’s Anatomy or the Underworld films, and who I know from the horror film The Strangers, is the star of R.J. Decker, the new quirky detective series based on the Carl Hiaasen novel Double Whammy.The hour-long drama stars Speedman as, you guessed it, R.J. Decker. Here, Speedman steps into his best disheveled self, playing a defamed newspaper photographer-turned-ex-con who forges a new life in South Florida as a private investigator. Technically, the show is a procedural that follows Decker as he investigates offbeat cases each week. Thanks to the…