GAITHERSBURG, Md. (AP) — It's been nearly 40 years since sisters Sheila and Katherine Lyon paid a weekday visit to a Maryland shopping mall — and never returned home.
The chilling 1975 disappearance of the girls, ages 12 and 10, set off an exhaustive search for potential suspects, spread panic throughout the region and has flummoxed police investigators for decades. On Tuesday, police in Montgomery County, Md., announced a potential breakthrough in the case, saying they had identified a new person of interest — a convicted child sex offender in a Delaware prison.
Police said they've established that 57-year-old Lloyd Lee Welch was at the mall the day the girls vanished and was seen paying attention to them. Welch, whom police describe as a former ride operator for a carnival company and a drifter who traveled the U.S. and often stayed in homeless shelters, has convictions in multiple states for sexually assaulting young girls and has been locked up in Delaware for more than 15 years.
But the case is based so far on circumstantial rather than physical evidence, which is why police say they're seeking the public's help to learn more about the man and his activities as they try to assemble enough information for a potential criminal prosecution.
"If we were able to charge somebody, we'd have done it," county Police Chief J. Thomas Manger said at a news conference.
An attorney for Welch could not immediately be found. A lawyer who previously represented him in a Delaware child sex assault case did not immediately return a call seeking comment.
Manger said Welch was not an original suspect but recently emerged as a person of interest after investigators with "fresh eyes" reviewed his criminal history and determined he was at the mall when the girls went missing and may have had contact with them. He refused to say how police had reached that conclusion or what, if anything, Welch has said to detectives trying to interview him.
The police chief also cited apparent physical similarities between a police mug shot of Welch taken after a 1977 arrest and a sketch, based on a witness' account, of a man who appeared fixated on the girls at the mall, then known as the Wheaton Plaza.
The Lyon girls — one bespectacled in a blue sweatshirt, blue jeans and brown shoes, the other in a red jacket, knit hat and flowered blue shirt — went missing on March 25, 1975, after walking for lunch to the nearby mall. A missing person bulletin issued at the time said there was "nothing to indicate runaway situation" and warned that foul play was possibly involved.
Since then, detectives have worked continuously on the case, pursuing innumerable leads in multiple states, chasing connections to child sex crimes investigations, interviewing witnesses, enlisting dogs to scour woods and, in at least one case, digging up the backyard of a home in a futile search for the bodies.
In a statement distributed by police Tuesday, the Lyon family thanked the public for its continued interest but requested privacy.
"The fact that so many people still care about this case means a great deal to us," the family said.
Police on Tuesday released a timeline including about two dozen U.S. locations, from California to Iowa to South Carolina, where Welch is believed to have visited or lived between 1974 and 1997. Authorities are investigating whether Welch, who is originally from the Washington, D.C., area and was arrested for burglary several blocks from the mall in the mid-1970s, committed other crimes in those places.
He was known to hitchhike in and around the region, spent time in hotels and homeless shelters and worked in different locations as a landscaper and for a carnival company that often set up at malls around the country, police said.
"We know we're asking for people to remember things they may not want to think about," said Stephen Vogt, head of the FBI's Maryland office, adding that it's not easy for sex assault victims to come forward. But he said the information could help investigators solve the case.
This isn't the first time that police have singled out a person of interest.
In 1987, for instance, detectives pursued a possible link involving a convicted child molester imprisoned in North Carolina but did not bring any charges. Police have also earlier said the girls were seen at the mall with a man who had a briefcase containing a tape recorder, according to news accounts, though Manger said Welch is not believed to be the same person.
He said the department was committed to finding justice for the family.
"These girls deserve a proper burial, frankly," Manger said.
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