GEORGETOWN — Solving a mystery that has baffled investigators for 40 years, Williamson County Sheriff Robert Chody announced Wednesday that the homicide victim found in 1979 and known only as "Orange Socks" was 23-year-old Debra Jackson of Abilene, who left home in 1977.

The sheriff's office got a break in the case when Jackson's sister saw a composite sketch of Jackson on TV that was released by the sheriff's office in June, Chody said. Officials found out this past weekend that the sister's DNA matched Jackson's.

The investigation was known as the “Orange Socks case" because Jackson, who had been strangled, was found nude except for orange socks. She was discovered in a concrete culvert on Interstate 35 north of FM 972 in Georgetown on Halloween Day 1979.

Jackson left Abilene in 1977 and in 1978 went to Amarillo, where she worked at a Ramada Inn, Chody said at a news conference Wednesday. She also worked in 1978 at an assisted living center in Azle, northwest of Fort Worth.

Scars on her lower legs shown in autopsy photos are consistent with impetigo scars family described from her childhood, the sheriff said. Impetigo is a bacterial infection. Her family also recognized her abnormally long toes and uniquely shaped earlobes, Chody said.

They thought she had run away from home and was "doing OK," said sheriff's Sgt. John Pokorny. She was never reported as missing, officials said.

Chody said it was too early to identify a suspect in her death. "I spoke to a family member," he said. "They said, 'We can let her rest now.’”

After Jackson's sister saw her sketch on television, she provided her DNA to a nonprofit group called the DNA Doe Project that was working with the sheriff's office.

Jackson's DNA and her sister's DNA test results matched when they were loaded into a genealogy database called GEDmatch, said Jackie Jones, a member of the DNA Doe Project who spoke at the press conference.

Male DNA from Jackson's fingernail clippings is still being investigated, Chody said. "We're hoping there's a witness still alive and says, ‘Hey, I knew Debra,’” he said.

He asked anyone who knew Jackson after she left Abilene to call detectives at 512-943-5204.

Chody said identifying the victim was "a big deal," and he praised the cold case unit. "We haven't solved the case, but we solved something not done in 40 years." Chody formed the cold case unit a few months after he took office in 2017. It consists of retired investigators who volunteer their time. Chody said they worked more than 1,000 hours on the Jackson case.

The case was featured twice on the “America’s Most Wanted” TV show. Investigators have described the woman as being in her mid-20s, white, 5 feet 9 inches tall and weighing 135 to 140 pounds. Her hair was brown with a reddish tint and she had hazel eyes and pierced ears. She was wearing an oval-shaped abalone shell and silver ring when she died.

Henry Lee Lucas, who once confessed to hundreds of murders nationwide but later recanted them all, was convicted in 1984 of strangling the woman.

He received the death sentence in her slaying, but it was commuted to life in prison after doubts were raised about his confession, including an investigation that showed he might have been in Florida when the woman was killed. Lucas died in 2001 in prison.

Chody declined to comment Wednesday about whether Lucas was still considered a suspect in the Jackson case.