PORTLAND, Ore. (KOIN) — Oregon State Police have solved the 1979 cold case murder of a Salem teen.

Janie Landers was a patient at the now closed Fairview Training Center in Salem. She struggled with learning challenges and behavior issues. Officials say at 18 years old, Landers functioned at the level of an 8-year-old.

On March 9, 1979, she disappeared.

Her body was found dumped near Silver Falls State Park on March 14, five days after her disappearance.

Landers had been brutally beaten and stabbed multiple times, according to detectives. An autopsy showed defensive wounds and deep cuts around her neck. Landers is believed to have died on the day she disappeared.Police interviewed people who knew Landers at Fairview and outside of the facility, but the case went cold.

Landers’ little sister Joyce, who was just 13 when Janie was murdered, urged detectives to reopen the case over the next few decades. They obliged several times, but without any results.

In March of 2015, Joyce asked police to try again. Her father was now 82 years old and Joyce hoped they could find justice for Janie while he was still alive.

The case was handed off to Detective Steve Hinkle. He scoured hundreds of pages of police reports, physical evidence, autopsy findings and scene photos. He contacted the original witnesses who were still alive and met with the detectives who had previously tried to solve the case.

“It needed to be solved,” Hinkle said. “It was a vulnerable young girl who got murdered for no reason.”

Since Landers had clearly fought for her life, Hinkle suspected the killer had been injured in the process. And in April of 2016, forensic scientists confirmed that a blood stain on Landers’ clothes contained a man’s DNA.

It matched that of Gerald Kenneth Dunlap, a twice-convicted sex offender who died in an Oregon prison in 2002.

Dunlap sorted and washed laundry at Fairview at the time of Landers’ disappearance, and he was later fired for inappropriate contact with female patients, according to the Marion County District Attorney’s Office.

“This case would have never have been solved were it not for the dedicated work of the Oregon State Police Detectives, the persistence of a little sister who never forgot for nearly four decades, and the courage of a prior victim to report her abuser and withstand the rigors of a trial,” Deputy District Attorney Paige Clarkson wrote in her report. “It is because of her that Dunlap could never hurt anyone again and, most importantly for this case, his DNA was on file.”

On October 30, 2017, Hinkle returned one of Landers’ earrings and 2 small hair ties to her family, all that remained from that 1979 day.

According to Clarkson’s report, Landers’ sister Joyce Hooper said she’s relieved that the case is solved, and that now Janie can be at peace.

“Sometimes when people get in places like that, they get forgotten about,” Hooper said. “And I didn’t want anyone thinking that was the case with Janie.”