Cold case murder of Portland college student Barbara Mae Tucker, 19, is finally solved FOUR DECADES later: Killer faces life in prison after DNA collected from discarded gum secured conviction

The cold case murder of a 19-year-old college student in Oregon was cracked over four decades later after DNA from a piece of discarded gum secured a conviction.

On Friday, Robert Arthur Plympton, 60, was found guilty of murdering Barbara May Tucker the night of January 15, 1980, as she walked across the Mount Hood Community College campus.

Suspicions were raised when she never arrived at class. The following morning, students discovered her cold, partially naked body near a campus parking lot. There were signs she been sexually assaulted and had fought against her assailant.

A medical examiner determined the teen had been raped and beaten to death. 

Friday's ruling came after a three-week bench trial in Portland. According to The Oregonian, Tucker's case was the oldest cold-case murder in the city of Gresham.

Robert Arthur Plympton, 60, was found guilty of murdering Barbara May Tucker, 19, in January 1980, when he was just 16 years old himself

Tucker was heading to a night class at Mount Hood Community College but never arrived. Other students discovered her half-clothed body the following morning

Decades passed before investigators were able to identify a suspect and make an arrest.

But the advancement of DNA sequencing technology proved advantageous. In 2000, vaginal swabs that had been taken during Tucker’s autopsy were sent to the Oregon State Police Crime Lab to develop a DNA profile.

In 2021, Parabon NanoLabs, a DNA phenotyping company, identified Plympton as 'a likely contributor to the unknown DNA profile developed in 2000,' the Multnomah County district attorney’s office said.

Plympton had a checkered criminal past including a conviction for second-degree kidnapping five years after Tucker's death, according to the Oregon Department of Corrections. 

Detectives with the Gresham Police Department learned that Plympton was living in Troutdale and began monitoring him.

When Plympton spat a piece of chewing gum onto the ground, they collected it and submitted it to a state police crime lab. 

'The lab determined the DNA profile developed from the chewing gum matched the DNA profile developed from Ms. Tucker’s vaginal swabs,' the district attorney’s office said. 

This method of DNA collection is similar to a step taken in the case of accused serial killer Rex Heuermann, where investigators matched DNA on a discarded pizza crust with evidence from the burlap used to bind one of the Gilgo Beach murder victims.

The teen had been beaten to death, and the medical examiner's office determined she had been sexually assaulted

Investigators began monitoring Plympton in 2021, after advancements in DNA sequencing technology matched a sample from a discarded piece of gum to a profile developed in 2000

Plympton was just 16 when Tucker was assaulted and beaten to death.

Witnesses reported seeing her with a man the night of her murder, and several people recalled seeing her run into the street waving her arms, possibly trying to flag down help.

Plympton was arrested on June 8, 2021, as he drove away from the home he shared with his wife and son.

He pleaded not guilty to the murder charges at his arraignment that month. 

There was no evidence that Plympton and Tucker had known each other, Multnomah County Chief Deputy District Attorney Kirsten Snowden said at trial.

Judge Amy Baggio of Multnomah County Circuit Court found the 60-year-old guilty of one count of first-degree murder and four counts of 'different theories of murder in the second degree,' the district attorney's office said. 

'To be clear, this court has zero doubt whatsoever that Robert Plympton beat Barbara Tucker in her head and face until she died,' Baggio said in court. 'He did.'

Plympton was charged with rape and sex abuse in addition to the counts of first- and second-degree murder. 

Despite evidence that Tucker had been sexually assaulted, Plympton was not convicted on these charges, as prosecutors failed to prove beyond a reasonable doubt the abuse happened while she was alive.

During the trial, Plympton maintained his innocence, claiming he did not match the description of a man seen pulling the victim into the bushes. 

Defense attorney Stephen Houze said there was 'unmistakable, unavoidable reasonable doubt' about who killed Tucker.

He pointed to witnesses' descriptions of the man who was seen with Tucker - who was nearly six feet tall - as being about her height or taller. Plympton's booking records list his height as 5'9.

Houze also asserted that investigators never tested Tucker’s clothing for DNA evidence.

In a statement Tuesday, Plympton's lawyers vowed to appeal the ruling, stating they were 'confident that his convictions will be overturned.'

In 2021, after Plympton's arrest Susan Pater said she was disturbed by the fact that her sister's killer had lived nearby for so long

Plympton was found guilty of one count of first-degree murder and four counts of 'different theories of murder in the second degree.' He was not convicted on rape or sex abuse charges

Two of Tucker's relatives cried and embraced after the verdict was read.

Her older sister, Alice Juan, said in a statement to The New York Times that her family was 'thrilled that this was finally solved.'

'I thought it might not be as the years went on, but Barbie was a special little girl,' she said, describing Tucker as 'bright, bubbly, caring, all of those things.'

At the time of Plympton's arrest in 2021, Susan Pater, one of Tucker’s three sisters, told KATU News that detectives had promised to hunt down the killer.

'I was just totally taken aback. It was amazing,' Pater said. 'It was really good news. I’d given up. Although I think of her almost every night.'

She said she was struggling to come to terms with the fact that her sister's murderer had been living close by for so long.

'That somehow it didn’t slip, or come out of his mouth, that somebody might have done something, that he was able to carry on with his life after taking another. Yeah, it’s very hard,' she said.

'Could he sleep at night? I have a feeling he probably could.'

Plympton remains in custody at the Multnomah County Detention Center.

He is scheduled to be sentenced on June 21 and faces a life sentence with the possibility of parole after 30 years on the first-degree murder charge.