Police always suspected David Joseph Carpenter was the killer, but they could never prove it until now.
Mary Frances Bennett was murdered on October 21, 1979.
The 23-year-old left her apartment on the 400 block of 44th Avenue for a late Sunday afternoon jog. She went to her favorite place just north of Painted Rock at Lands End.
Her body was found later that evening.
"Several people walking in the area found a set of bloody keys, walked down the trail a little further and that's where they found Mary Beth," homicide inspector Joe Toomey recalled.
She was in a wooded area covered with twigs and dirt, stabbed numerous times.
Last December, 30 years later, the San Francisco police cold case team decided to take another look at the unsolved murder. Investigators took the old evidence including DNA samples that police had preserved and sent them to a lab.
"We entered it into the state computer and we were informed that it came back to David Joseph Carpenter," Toomey said.
Carpenter is best known as the "Trailside Killer." He terrorized the Bay Area in the late 70s and early 80s, raping and murdering his victims in parks and hiking trails in Marin and Santa Cruz counties.
He was finally arrested in 1981 and convicted of two murders for which he got the death penalty. Four years later, he was convicted of five more murders and is now on death row at San Quentin.
Toomey, who interviewed him last month, told ABC7, "He denied knowing her and he denied killing her."
The murders for which Carpenter was convicted were committed in the early 80s. Mary Bennett's murder in 1979 is now the first documented killing by Carpenter.
Bennett's parents past away some time ago, but her brother Joseph, a school superintendent in Montana, says he is relieved and satisfied that the case has finally been solved.