An expert warns that more serial killers could be hiding in plain sight after advances in DNA technology helped identify a Pennsylvania man authorities say killed at least two women in the 1970s.
At a news conference Thursday, Pennsylvania State Police identified James Richard Clark Sr. as the man who sexually assaulted and strangled Brenda Ritter, 18, and Susan Rush, 21, during the 1970s.
Rush disappeared Nov. 24, 1976, after leaving a shopping mall, according to the City of Washington Police Department. She was expected to meet her family at church, but never arrived. The following morning, Thanksgiving Day, her brother found her car parked along a street. Her body was discovered inside the trunk.
Pennsylvania State Police identified James Richard Clark Sr., who died in 2023, as the man who killed Brenda Ritter and Susan Rush in the 1970s. (Pennsylvania State Police)
Ritter disappeared from her boyfriend’s home in 1977, police said. Her body was later found on a hillside. Authorities determined that she had been sexually assaulted and strangled.
Clark Sr. died of natural causes at age 66 on July 17, 2023.
In late 2018, evidence from Ritter’s killing was submitted to the state police crime lab, where analysts developed a DNA profile belonging to an unidentified male. Investigators entered the profile into the FBI’s Combined DNA Index System, known as CODIS, but weekly searches produced no match. Testing conducted at Cybergenetics’ laboratory in May 2025 indicated that the same man was responsible for both women’s deaths.
Police said Clark left DNA evidence at both crime scenes. Advances in testing at several laboratories, including Identifinders International, helped investigators focus on him before additional testing confirmed the connection.
Brenda Ritter, 18, disappeared from her boyfriend’s house in 1977 and was later found on a hillside after being sexually assaulted and strangled, police said. (Pennsylvania State Police)
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Police said Clark was 20 when Ritter was killed and 19 at the time of Rush’s death.
Pennsylvania State Police Cpl. James Petrosky said he believes there may be additional victims.
“I believe that once you’re a serial killer, you’re always a serial killer. I believe there could potentially be more victims out there,” Petrosky said.
Dr. Kris Mohandie, a former LAPD psychologist and FBI behavioral analysis consultant, told News Media that it is “normal” for the number of known victims to be lower than a serial killer’s actual toll. He said advances in technology frequently help investigators identify previously unconnected crimes.
“I think it’s normal and normative that the number of known cases is always less than what has been detected,” Mohandie said. “These kind of guys often have more victims out there than they’ve been known to be connected to. The reality is that there are usually more crimes attributable to serial offenders than they’re ever held to account for.”
Susan Rush, 21, disappeared after leaving a shopping mall on Nov. 24, 1976. Police said her body was found the next morning inside the trunk of her car. (Pennsylvania State Police)
Mohandie said serial killers can also disappear from the radar for years. In some cases, they may sense that investigators are closing in; in others, family responsibilities or other changes in their lives may contribute to a period of inactivity.
“There are a lot of cases where they do go dormant, what we call a cooling off period, and that can be because they realize it’s too hot for them to continue to offend, that they’ll get caught, so it’s a strategy to avoid being captured. It may mean that they’ve had a close call with being captured, and it spooked them, so they’ll go quiet for a while because of that,” he said.