DNA advances identify Pennsylvania man in two 1970s killings

New DNA techniques helped investigators identify a Pennsylvania man they believe killed at least two women in the 1970s. A forensic expert says cases like this raise the possibility that other victims of serial killers may remain unidentified.

Pennsylvania State Police said Thursday that James Richard Clark Sr. sexually assaulted and strangled Brenda Ritter, 18, and Susan Rush, 21.

Rush disappeared on Nov. 24, 1976, after leaving a shopping mall. She was expected to meet her family at church but never arrived. The next morning, her brother found her car parked on a street. Her body was later discovered in the trunk.

Ritter vanished from her boyfriend’s home in 1977. Her body was found on a hillside, and investigators determined she had been sexually assaulted and strangled.

Clark died of natural causes on July 17, 2023, at age 66. Police said he was 19 when Rush was killed and 20 at the time of Ritter’s death.

Evidence from Ritter’s killing was sent to the state police crime lab in late 2018, producing a DNA profile from an unidentified man. Investigators entered the profile into the FBI’s CODIS database, which was searched weekly, but it returned no match. Testing at Cybergenetics in May 2025 indicated that the same man was responsible for both women’s deaths.

Police said Clark left DNA at both crime scenes. Further testing at multiple laboratories, including Identifinders International, helped investigators focus on him and ultimately confirm the match.

Pennsylvania State Police Cpl. James Petrosky said investigators believe there could be more victims. “I believe that once you’re a serial killer, you’re always a serial killer,” he said. “There could potentially be more victims out there.”

Dr. Kris Mohandie, a former Los Angeles Police Department psychologist and FBI behavioral analysis consultant, said the number of crimes linked to a serial killer often falls short of the actual total. New technology, he noted, can help investigators connect cases years later.

Mohandie also said serial offenders may stop for extended periods. They might worry that police are closing in, or become focused on other parts of their lives, such as raising a family.

Some offenders, he said, enter what investigators call a “cooling-off period” after deciding that continuing to offend could lead to capture. A close call with police can also frighten them into staying quiet for a time.