Here is a nice meta-analysis of 80 studies, 22181 subjects: http://www.ncbi.nlm.nih.gov/pubmed/18206060 Note that re-offending dropped --by 37%. That means 63% went on to re-offend. I wonder if you would feel the same way if one of your loved ones was the one he did kill. Some risks constitute "never events"; we should strive for them to never happen. "Less likely" is not enough if you or your loved one drew the short straw.