Dear LFTP: should I report a crime confessed in group therapy?

• What is my ethical responsibility when I hear a crime confessed in group therapy?

A listener attending Narcotics Anonymous heard a man confess to dropping a cinder block on a boy's head at age 12 and asks whether to tell the police. The hosts say: talk to the man first and tell him to make it right, and as a non-leader participant with no confidentiality oath, don't hesitate to report it yourself. The secular answer says it may be too old to accomplish anything and suggests talking to the group leader.