Real Name: Diana Robertson
Nicknames: No known nicknames
Location: Tacoma, Washington
Date: December 15, 1985
Details: In December 1985, 36-year-old trapper Mike Riemer took his girlfriend, Diana Robertson, and their daughter, Crystal, into the woods near Tacoma, Washington to look for a Christmas tree. That afternoon, Crystal was found wandering around a department store without her parents. She was later identified after her photo was placed in the newspaper and her maternal grandmother recognized her. Mike and Diana had vanished without a trace, and all Crystal could tell police was that "Mommy is in the trees". Two months later, Diana's body was found deep in the forest around Elbe, Washington. She had been stabbed seventeen times and had a tube sock tied around her neck; there was no sign of Mike. His truck, which was nearby, had blood stains on the front seat and a note on the dashboard that read, "I love you, Diana." Although her mother believed that it was his handwriting, it could not be confirmed. Police believed him to be responsible for her murder as well as a double murder that occurred in the same woods four months earlier. A man named Stephen Harkins was found shot to death in his sleeping bag. His companion, Ruth Cooper, was found strangled two months later. They were camping in the same area where Mike set his traps. Both Ruth and Diane had been killed with the tube sock tied in the same way. Police considered two theories; the first was that an unknown serial killer had killed both couples, and then hid Mike's body. The other theory was that Mike himself was the serial killer. He apparently had a history of domestic violence, and this, along with other evidence, was enough for police to issue a warrant for his arrest. Police had not been able to determine if he was alive or dead, or if he was the killer or a victim. The murders remain unsolved.
Suspects: Mike was the prime suspect in Diana's, Stephen's, and Ruth's murders. He was 6'0", 180 pounds, has blue eyes, brown hair, a scar on his upper lip, and was a skilled outdoors man who was thought to be living off the land. He was then eliminated as a suspect when his skull was found in the same forest years later. It's now believed an unidentified serial killer murdered the couple, as other couples were murdered before the Robertsons.
Extra Notes: This case first on the September 6, 1989 episode.
Results: Unresolved. In March 2011, Mike's skull was found. The cause of his death is publicly unknown. Police have since ruled him out as a suspect in the double murder, and authorities now believe that an unknown serial killer may be responsible for the Harkins/Cooper and Robertson/Riemer murders