Dateline's investigation of Keith Hunter Jesperson, the "Happy Face Killer." In 1995 Jesperson pleaded guilty to the murder of three women. But when behind bars, Jesperson started playing a cat and mouse game with prosecutors, confessing to crimes where others had been caught and convicted. He now claims he's killed more than 166 men and women across the country while working as a long-haul trucker. Dateline's story proves conclusively that Jesperson was lying.