Authorities say they have solved the 1976 rape and killing of the ex-wife of Righteous Brothers singer Bill Medley, using a controversial DNA testing method.
Los Angeles County Sheriff's Department said investigators had identified Karen Klass' killer by using DNA from a relative of the suspect.
The case "was solved through the use of familial DNA, which identified the killer", the department said, but provided no other details.
Ms Klaas, 32, was sexually assaulted and strangled in January 1976 as she returned to her home in Hermosa Beach, near Los Angeles.
She never regained consciousness and died in a hospital a few days later.
The DNA technique, which has raised ethical issues in the forensics community, allows investigators to search law enforcement databases to identify likely relatives of the person who may have committed the crime.
Police have argued the technique can provide investigators with valuable leads.
A sheriff's spokeswoman would not say whether an arrest had been made and declined to identify the suspect.
Los Angeles County sheriff Jim McDonnell, district attorney Jackie Lacey and other officials are expected to release more information on Monday.
Sheriff's investigators, seeking help from the public in 2009, said two witnesses spotted a shaggy-haired, bearded man in a trench coat and blue jeans leaving the house, but the man was never seen again.
Officials said they were able to put together a DNA profile of Ms Klaas' killer, but in 2009 said it had not matched anyone in the national database.