Michael Mullen, Sex Offender Vigilante
An investigation of known sex offenders in the region eventually led to Duncan, and was arrested late in March 2005 after the boy and other witnesses picked him out in a photo lineup.
He was charged with second-degree criminal sexual conduct, which carries a maximum sentence of 25 years under Minnesota law. As a repeat offender, Duncan likely was facing a long prison term if convicted.
Those in the university computer science department were stunned when a story about the allegations against Duncan appeared in the local paper.
A Fargo businessman posted $15,000 bail, and Duncan was released on April 5. The Minnesota judge later said that he was unaware of the disturbing details of Duncan's rape of the teenager in 1980. He said he would have set a higher bail had he known.
A week later, on April 13, Duncan went on a peculiar shopping expedition at a Wal-Mart store in Fargo.
Authorities said he spent $732 on night-vision goggles, a palm-sized camcorder, blank videotapes, a radar detector and a car battery.
On April 20, Duncan made a final contact with a pre-trial probation officer in Minnesota. He stopped by the computer science department on about the same day, looking for a lost cell phone. He walked out and wasn't seen again, fleeing in his leased red Jeep.
But the Wal-Mart purchases indicated that he had made plans.