CSI was a rerun tonight (which I hadn't realized until the credits came on, and I saw that they were last season's credits). I had only seen the show on its original airing, so I watched it again, and didn't remember anything about the identity of the murderer, etc. All the revelations came as total surprises.
This must have come on last season during either SOMETHING'S AFOOT or NUNCRACKERS when I was distracted with the shows enough to not concentrate much on any TV I was recording.