"Anatomy of a Murder" is one of those episodes which was decent but unremarkable. The case isn't original or clever, but it's logical and has more than one component to it. The stuff with Castle, his ex-wife, and Alexis shed some light on Castle, but was plain. Beckett declares that she'd save Castle from prison, but we already knew she would.
Honestly, I don't really have anything else to say about the episode. In its third season, Castle often ends up around the same ballpark as this episode, and there's not much worth commenting on anymore.
Score: 8.5/10