CBS

Season 9: Episode 21 - If I Had a Hammer

If I Had a Hammer: Catherine is called in by Eckle to revisit a crime that took place nine years prior. She was a newbie at the time. She put away a young man for murder. Nine years later he has educated himself in prison -- and is claiming that the conviction was faulty. The CSIs have to re-prove the case - and re-convict this man. Catherine suffers a crisis of confidence when it looks as if he may have been innocent and working with an accomplice. In the end it turns out there was an accomplice -- his high school sweetheart, who is now a upscale suburban mom. He protected her all these years, but now it is revealed that she was the one that actually committed the murder.