Forty-two years after Las Vegas teenager Kim Bryant was sexually assaulted and murdered, police say that DNA evidence has identified her killer.

Kim Bryant, 16, disappeared after failing to meet her boyfriend at a Dairy Queen, and her body was found in a desert area three weeks later.

Now investigators believe that Johnny Peterson, who was 19 at the time and died in 1993, is her murderer.

DNA from her body was recently tested by a Texas lab, and it led to a relative who agreed to give a sample that showed a match, officials said.

“He was never on the radar as a suspect,” Las Vegas Metropolitan Police Department homicide Lt. Ray Spencer said at a news conference Monday.

Kim was reported missing Jan. 26, 1979, after she never returned home from Western High School, police said. Her boyfriend said he was supposed to pick her up at a Dairy Queen that morning but when he got there, she was not there.

Her body was found in a desert area on Feb. 20 of that year, and sperm was recovered during autopsy, Spencer said, but the case was eventually classified as a cold case.

In 2008 it was tested but no profile was found, Kim Murga, director of laboratory services for the police department, said. It was tested again in January and a foreign male profile was found but it didn’t generate any hits in a DNA index, she said.

A donation by a local philanthropist, Justin Woo, led to advanced genetic testing through a Texas lab, officials said. That led to a relative who agreed to be tested and proved a family tie.

Michael Vogen, director of case management at the lab company Othram, said that it developed a large profile and narrowed it down.

“We upload that into various databases, and we find distantly related people to that DNA, and we slowly include or exclude them as being closely related,” he said. “We work that family tree.”

Edward Elliott, Kim’s father, in a statement read by police Monday thanked investigators and Woo.

“Kim was a beautiful girl with a bright future, and it makes me happy that something is being done to help solve cases such as hers,” he said in the statement.

Peterson lived in Las Vegas at the time and at one point attended Western High School, but he was not a student there when Kim was killed, Spencer said. He was arrested in a different sexual assault in 1980 but that case was dismissed, Spencer said.

In 2018, investigators in California made an arrest in the decades-old “Golden State Killer” cases from the 1970s and 80s, after genealogy and DNA from crime scenes pointed them towards a suspect.

Former police officer Joseph DeAngelo, now 76, was arrested based on DNA discovered from a discarded tissue, but investigators narrowed in on him based in part on a genealogical website, officials have said.

DeAngelo is serving life in prison without parole after pleading guilty to 13 counts of murder and 13 rape-related charges. He admitted to dozens more sexual assaults for which the statute of limitations had expired.