The Los Angeles County Sheriff's Department has identified the man they say killed the former wife of Righteous Brothers singer Bill Medley.
The 32-year-old was attacked January 30, 1976 as she returned to her home in the Hermosa Beach neighborhood, was sexually assaulted and strangled with her pantyhose.
Over the years, it became a cold case until this past weekend when investigators announced they now believe they know who did it, using the familial DNA method, which has been viewed as controversial.
It compares samples of DNA taken from the crime scene with that of a "first-degree relative", Capt. Steve Katz said. Troyer has been linked to other sexual assaults in California, police say, but was never required to submit his DNA to a database. Her husband was ruled out as a suspect, authorities said.
As he spoke, Medley was surrounded by Klaas' two sons and investigators who had worked on the case, some since Day One.
There, the 32-year-old mother of two was sexually assaulted and strangled with her own pantyhose.
She never regained consciousness and died four days later at a hospital.
"It's just nice to close the book on this", Medley said at the news conference.
Although DNA testing was not used at that time, police had gathered and recorded items they hoped might be helpful in future, which turned out to be the key to solving the murder decades later.
"There's been a voice in the back of my head - probably Karen's - telling me since about 20 years ago to drop it, let it go", Medley said.
"It's incredible because I did not believe we would ever identify who had committed this crime", Darrin, Klaas' son, added.
Mr McDonnell said: "Because of the familial DNA search, detectives were able to link Troyer's DNA and positively confirm his identity as the killer".
"If practiced routinely, we would be subjecting hundreds of thousands of innocent people who happen to be relatives of individuals in the Federal Bureau of Investigation database to lifelong genetic surveillance", Tania Simoncelli, science adviser to the American Civil Liberties Union, told The Post at the time.
A man was seen leaving her home around the time of the crime, but her killer was not found. As investigators began to hone in on him as a possible suspect past year, they were able to obtain a sample of his DNA that was held in the Orange County coroner's office and conclusively link him to Klaas' slaying, Katz said.
"He retired and I did a little favor for his retirement, so he came to me and said, 'I am going to get this solved for you, ' " Medley remembers of detective Darrell Hardin. Both stood by law enforcement during the announcement Monday. "She would have been an incredible grandma [as well]".