This is one of the cases featured on the DVD box set Unsolved Mysteries: Bizarre Murders. It has been haunting me ever since I learned about it, but I can't find any other information on it. Does anyone know anything further?
DAKOTA'S DOUBLE DEATH - (South Dakota) Three young friends found themselves in a terrible accident when their car jumped the highway and came to rest in a ditch. By the time help arrived, two of the victims, 20-year-old Arnold Archambeau and his girlfriend, 19-year-old Ruby Bruguier, had mysteriously wandered off.
For three months there were no signs of the young couple. Then, on March 10, 1993, the body of Ruby Bruguier was found floating in the ditch, just 75 feet from the crash site. The next day, Arnold's body turned up a few yards away. However, the two bodies were in very different states of decomposition. Police are convinced that the bodies were not there at the time of the accident.
A friend of the young couple came forward stating that he had seen Arnold Archambeau during the three-month period between the car crash and the discovery of the bodies. The friend successfully passed a polygraph examination regarding his claim.