Diana Robertson

Mike Riemer & Diana Robertson

Mike Riemer & Diana Robertson

A serial killer is suspected in the murder of a young mother.

On the morning of December 12, 1985, Mike Riemer, his girlfriend Diana and their daughter, Crystal, set out for a day in the mountains near Tacoma, Washington.  Diana had just turned 21 and had known her 36-year-old boyfriend since she was 17.  The couple drove up into the forest south of Tacoma, a scenic region often frequented by campers and nature lovers.  They planned on finding a Christmas tree, and as Mike was a trapper, he intended to check his animal traps.

Later that same afternoon, Crystal was found at a department store near Tacoma.  She seemed stunned, silent, and her parents were nowhere to be found.  After being checked at a local hospital, Crystal was sent to a temporary foster home.  Three days later, after being recognized from a news broadcast, Crystal was identified by Diana’s mother, Louise Conrad:

“And as soon as she saw me, she put her arms out and said, ‘Gramma.’  And they put her down and she ran to me and, and I’ve had her ever since.”

Crystal’s parents had vanished without a trace.  When Crystal was asked where her parents were, all she could say was “Mommy is in the trees.”  Four months earlier, the forest area where her parents disappeared had been the scene of two brutal murders.  Initially, police made no connection between the couple’s disappearance and these murders.  But soon a connection would prove inescapable.  A massive search was launched the same weekend the couple disappeared.  Mike’s best friend, Steve Tew, scoured the countryside on the ground and from the air:

“We searched from the spot where Mike would normally start his trap plans and we followed the whole, trap plan.  And we searched for probably two or three hours… nothing.”

Diana was found murdered

Diana was found murdered

Then, two months after the couple disappeared, a man walking his dog deep in a forest near Elbe, Washington, discovered the body of Diana Robertson.  Crystal was correct when she said that her mother was “in the trees.”  Diana Robertson was lying dead in the forest alongside Mike’s truck.  She had been stabbed 17 times and a tube sock was tied around her neck.  There was no sign of Riemer.  When Detective David Neiser of the Lewis County Sheriff’s Department searched Mike’s truck, he found bloodstains on the front seat:

“Unfortunately, after two months and about two weeks, some of the characteristics of the blood were lost.  And they were not able to tell us what the blood type was.  But they were able to tell us the blood was human.”

Police then found another baffling clue.  Displayed prominently in the truck’s cab was an envelope that read, “I love you, Diana.”  Diana’s mother Louise believed the handwriting was Mike’s:

“I have cards that he had given to her on different holidays and things… he signed exactly the same way.”

But according to Detective Neiser, the FBI’s analysis of the handwriting came back inconclusive:

“Why did someone put that there?  Was it Michael Riemer as a final,’goodbye Diana, I’m sorry?’  Or was it someone who put it there to throw off the authorities and make them think that.”

Police believed that this killing was possibly connected to a double murder that had occurred four months earlier, just 15 miles from where Diana Robertson was discovered.  These murders occurred in Pierce County, an area where Mike Riemer was known to set his animal traps.  A man named Stephen Harkins was found dead in his sleeping bag, shot in the forehead.  His companion, Ruth Cooper, was discovered two months later.  She too had been shot to death.  And like Diana, a tube sock had been tied around her neck.  According to Detective Neiser, the tube sock on Diana had been tied with exactly the same type of knot as in the earlier murder:

“At a later date, I asked to observe the sock, which was used around the neck of Ruth Cooper. And when he dumped it out on a desk in the evidence lab, the evidence technician let out a little whistle, because knowing nothing about the case, he could see that it was the same as the one I had brought with me from Diana Robertson.”

Police considered two theories.  One was that an unknown serial killer had murdered both couples, and then hid Riemer’s body.  The second theory was that Mike Riemer was the serial killer. Mike Riemer had a history of domestic violence.  According to Diana’s sister, Darlene Robertson, Riemer frequently beat Diana:

“He beat her up.  He took everything out on her.  He blamed her for things that he did.  If he was seeing somebody else, he would turn it around like Diana was seeing somebody else and justify it in his own mind.”

Police now had enough circumstantial evidence to issue a warrant for Riemer’s arrest.  But according to Detective Neiser, there was one glaring problem:

“We can’t prove he’s alive and we can’t prove he’s dead.  If we could show that he was dead, then it would be my belief that there’s an unidentified third party who’s going around killing people out there.  However, if we can prove that he’s alive, he immediately becomes a suspect and that changes the situation dramatically.”


The skull of Mike Riemer was discovered recently by a hiker about one mile from where Diana Robertson’s body had been found 25 years earlier.  No other traces of Riemer have been found, and his cause of death could not be determined.