The district court committed Duane Hart to the Minnesota Security Hospital as a sexual psychopathic personality and a sexually dangerous person. At the initial commitment hearing, the court heard testimony that Hart sexually assaulted at least ten victims, ages eight to fifteen. These assaults began in the early 1960s and continued until 1989 or 1990. Between 1968 and 1988, Hart was convicted of ten criminal offenses, most of which involved alcohol or drugs.
Hart committed hundreds of sexual assaults on at least ten young boys. He is a patterned sex offender whose victims are boys ages eight to fifteen. Hart repeatedly fondled, performed oral sex or made boys perform it on him, and performed anal intercourse. He used isolation, bribes, threats, force, and alcohol to commit these acts. Hart was often under the influence of chemicals during these assaults. Hart has refused treatment, has no relapse prevention plan, and minimizes his role in his sexual misconduct. Hart's problems are longstanding; he began drinking heavily at age six and was placed in residential treatment at age nine, where he was forcibly sodomized.
http://mn.findacase.com/research/wfrmDocViewer.aspx/xq/fac.19960220_0003.mn.htm/qx
I wonder how police could have ruled him out.