CARY — Marshall Dietz stopped at a traffic light outside of Washington, D.C., on April 7, 1975, and he glanced over at the car next to him.
What he saw in that backseat has haunted him for 39 years, at times taking him into a world of child-killers, Internet theorists, police suspects and strangers’ lives.
“It was Sheila,” said Dietz, 66, who now lives in Cary.
Dietz is convinced he saw Sheila Lyon, a 12-year-old girl who vanished from a suburban Washington shopping mall in March 1975, along with her 10-year-old sister Katherine. The girls are presumed dead, but an arrest was never made in the case.
The girl Dietz saw was lying on the backseat of a 1970 Ford Country Squire as if she were being held against her will, he said. He remembers that she looked up, revealing blue eyes and gold-rimmed glasses.
Dietz figures the driver of the car got spooked – he suspects another driver also spotted the girl – because the Ford ran the red light and sped away.
Dietz chased after the car but soon lost sight of it. Once he got to his job at IBM, he said, he called the police in Montgomery County, Md., and recounted his story.
That was pretty much the end of it for Dietz, for about three decades.
“I decided not to tell anyone,” he said.
The disappearance of the Lyon sisters shook the community and grabbed the attention of the media. But Dietz, who says he didn’t hear back from the police, put that day out of his mind. He didn’t want to stress his wife, Barbara.
But it all came back to him in a hurry when a police detective from Maryland called the Dietz home in Cary in 2005.
Dietz said he talked to the police a couple of times on the phone, but nothing really came of it. He wanted answers to what he saw that morning, so he started his own investigation.
He searched the Internet, reading blogs and theories about the case. His online chats with other people led him to James Mitchell “Mike” DeBardeleben, a career criminal who was eventually convicted on a slew of charges including counterfeiting and sex crimes.
Dietz even tried to reach out to an ex-wife of DeBardeleben, unsuccessfully. He wanted to visit DeBardeleben in prison, but he never got the chance.
DeBardeleben died in 2011, while he was serving his sentence at the Butner federal prison in North Carolina.
Blanca Kling of the Montgomery County Police Department said DeBardeleben is not a suspect in the case. She said the department was aware of DeBardeleben, but she would not elaborate.
In February, the department named a primary person of interest in the Lyon sisters’ disappearance after an examination of the cold case.
Lloyd Lee Welch, also known as Michael Welch, is a 57-year-old convicted sex offender. He worked for a traveling carnival during the 1970s.
Dietz is skeptical that Welch is the man he saw in the Ford on April 7, 1975. Welch would have been a teenager then. Dietz said the driver had flecks of gray in his dark hair, and a misshapen nose.
Dietz might never know the truth about what he saw. And the world might never know what happened to Sheila and Katherine Lyon.
But Dietz isn’t giving up, although his wife tells him to forget it and move on. They raised two kids together and now have two grandchildren.
“You make a choice,” Dietz said. “You can either carry it to your grave or try to change something.”
Mostly, he worries about families who lost children and never got answers.
And then there’s the guilt. What if he hadn’t lost track of that Ford? What if he could have done more?
Every year around this time, Dietz thinks a lot about Sheila – those blue eyes and gold-rimmed glasses, shown in a picture released by police.
“I didn’t see her because I was supposed to save her,” Dietz said. “I was supposed to remember and never give up.”
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