DNA Testing Is 40 Years Old

Oregon man found guilty of 1980 murder thanks to DNA

For years, no one knew who killed Barbara Mae Tucker.

She was killed on Jan. 15, 1980, and her body was found the following morning in a wooded area between Kane Road and a school parking lot in Gresham, Oregon, by students arriving for class.

While her case was cold for years, investigators gave the case a fresh look with advances in DNA technology.

In 2000, DNA swabs taken during her autopsy were sent to the Oregon State Police Crime Lab for analysis, and a DNA profile was made from the swabs.

Then in 2021, a genealogist from Parabon Nanolabs identified Robert Plympton as the likely “contributor to the unknown DNA profile developed in 2000,” the release said.

Police in Gresham found that Plympton was living in Troutdale and began to surveil him.

When they observed him spit out a piece of chewing gum onto the ground, detectives collected the gum and submitted it to the crime lab for analysis.

Following a bench trial from Feb. 26 to March 15, Judge Amy Baggio found Plympton guilty of murder and “four counts of different theories of murder in the second degree,” the district attorney’s office announced.

Though the medical examiner determined Tucker had been sexually assaulted, Plympton was not convicted of rape or sexual abuse because prosecutors failed to prove beyond a reasonable doubt it happened while she was alive, the judge said, according to The Associated Press.  

He remains in custody in Multnomah County with sentencing set for June 21.

DNA Testing Celebrates Its 40th Anniversary

British geneticist Sir Alec Jeffreys, discovered the technique of DNA testing to determine a genetic “fingerprint” in 1984. Jeffreys says he had his “eureka moment” while working at a laboratory in the Department of Genetics at the University of Leicester England. After looking at the X-ray film image of a DNA experiment which unexpectedly showed both similarities and differences between the DNA of different members of his technician’s family. Within about half an hour he realized the possible scope of DNA fingerprinting, which uses variations in the genetic code to identify individuals.

Jeffreys’ DNA method was first put to use in 1985 when he was asked to help in a disputed

immigration case to confirm the family identity of a British boy. The following year, in 1986, DNA fingerprinting was first used in a police identify a murderer.

The DNA of all human beings is nearly identical. Approximately 99.9% of the sequence of DNA is

in the exact same order. This determines common human features such as two eyes, ears on both sides of the head, and long bones in forearms and calves. Although looking at these parts of the DNA molecule might help us determine it is human DNA — rather than, say, banana DNA — it isn’t helpful in distinguishing one human from another.

There are, however, places on the human DNA molecule that are different. Of the approximately 3.2 billion base pairs in the human genome, some 3 million base pairs of DNA (about 0.10 percent of your entire genome) vary from person to person. These variations are at the core of DNA testing.

NBC News: Oregon Man Found Guilty of 1980 Murder

DNA Testing Was Discovered in 1984

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