Sheila Lyon, 12, and Katherine Lyon, 10, disappeared from Wheaton Plaza (now Westfield Wheaton) in the Washington D.C. suburbs on March 25, 1975. Lloyd Lee Welch, Jr., now 60, has pleaded guilty to their murders today and will serve two concurrent 48-year sentences for their deaths. The girls' bodies have never been found. (Photos: Courtesy of the Bedford County Sheriff's Office)

The 60-year-old suspect in the cold case killings of two young sisters who went missing from a Maryland mall over four decades ago has pleaded guilty and was sentenced to 48 years in prison for their murders. Lloyd Lee Welch, Jr., who was already serving a prison sentence for child sexual abuse in Delaware, was scheduled to stand trial today on the two counts of first-degree murder—for which he could have received the death penalty—but withdrew his trial request last week and instead entered his guilty plea, according to the Associated Press.

Sheila Lyon, 12, and Katherine Lyon, 10, disappeared from Wheaton Plaza (now Westfield Wheaton) in the Washington D.C. suburbs on March 25, 1975, and had last been seen that day at 2 p.m. walking between their mall and their home a half mile away, according to investigators. A massive search for the girls failed to turn up any trace of them, and their bodies were never found.

However, two potential suspects were identified by eyewitnesses who saw the girls at the mall: one was a 50-year-old man carrying a briefcase and tape recorder, seen talking to the girls shortly before they disappeared, and the other was a long-haired man in his late teens or early 20s who was seen staring at the girls while they shopped. The first man’s description and sketch were widely disseminated, according to the Washington Post, but the second man’s sketch, though published, did not seem to receive as much attention.

About a week after the girls’ disappearance, a then 18-year-old Welch approached a security guard at Wheaton Plaza and told him he had seen someone fitting the description of the middle-aged man police were looking for forcing the sisters into a car, the Post reports. Welch was interviewed by police, failed a polygraph, admitted to lying and was released. It wasn’t until 2013 when cold case investigators taking a fresh look at the disappearance noticed the resemblance between the second sketch and Welch, especially a 1977 mugshot of Welch following his arrest in an unrelated burglary.

Left: Sketch provided by witness who was at Wheaton Plaza on the day of the Lyon sisters disapperance. The witness stated that the person depicted in the sketch was fixated on the girls. Right: Montgomery County Police mugshot of Lloyd Welch, 1977. Welch was arrested for a residential burglary near Wheaton Plaza. (Credit: Courtesy of the Montgomery County Police Department)

Once investigators began to focus on Welch, more evidence began to emerge—Welch’s cousin, Henry Parker, told investigators that he helped Welch burn two heavy, red-stained and pungent-smelling duffel bags the same year that the disappearance occurred, according to the Washington Post. Additionally, Welch himself admitted to police that he left the mall with the girls the day they went missing.

In the 1970s, Welch was a carnival worker who travelled across the U.S. setting up rides at malls, according to investigators. By the time he became a person of interest in the Lyon case, he had multiple sex offense convictions for crimes committed against young girls in Virginia, Delaware and South Carolina. Welch had been in prison since 1997 for one of these crimes when he became a person of interest in 2014, at which time investigators released a timeline of his known whereabouts from the 70s to the 90s in the hopes of possibly finding more victims of his sex crimes. He was indicted on first-degree murder charges in July of 2015 and extradited to Bedford County, Virginia for trial, where it is believed he disposed of the girls’ bodies.

Lloyd Lee Welch, Jr. mugshot. (Photo: Courtesy of the Bedford County Sheriff's Office)

Had Welch’s murder case gone to trial, it would have been the oldest disappearance without the discovery of a body to result in a homicide trial, according to the Post. Instead, Welch took the guilty plea and received two 48-year sentences, one for each murder count, to run concurrently. He may be eligible for parole in about 25 years, according to WTOP.