Even though they're terrible people, I often root for murders to be set free. It might just be an irrational quirk that I have. If the person has done something that goes sadistic rather than just killing someone that they want dead, it's a different story. For example, I wish the worst upon those guys who recently got caught kidnapping girls and keeping them chained up at their house for 10 years.
Casey Anthony? Scott Peterson? They won't do any more harm. They might as well be free so that their families aren't in anguish for the rest of their lives.
The justice system as a whole still serves as a deterrent. So when individual people are set free, it doesn't really undermine the deterrence in any significant way. So I guess that's part of why I feel that way.
Maybe I would feel different it someone I knew was murdered. It might just be an irrational thing. But I'm just being honest about how I tend to feel.