Forensic DNA analysis is less accurate for some people, University of Oregon study finds

PORTLAND, Ore. (KOIN) – A new study led by researchers from the University of Oregon dug into limitations of a forensic tool used at crime scenes -- discovering one way that people may be incorrectly linked to a crime.

According to the study, published Sept. 18 in the journal iScience, forensic DNA analysis is less accurate among people with low genetic diversity.

In those cases, forensic DNA analysis is more likely to incorrectly link an innocent person to a crime, the researchers said.

Modern DNA analysis techniques are "extremely sensitive," the researchers explained. In some cases, scientists can gather trace amounts of DNA from shed skin cells and match that DNA to a person.

But that technique also means scientists are often looking at mixtures containing DNA from different people, such as everyone in a home who recently touched a door handle, researchers explained.

Even though scientists can look at the variation of genetic markers in a sample and compare it to a suspect's DNA, the study found some limitations.

University of Oregon data scientist, and lead researcher, Rori Rohlfs, and a team of undergraduate researchers at San Francisco State University, wanted to see how the accuracy of this approach is impacted by genetic ancestry.

The researchers looked at previously published genetic databases to see the frequency of certain genetic variants for groups of people with different genetic ancestry. Then, researchers used a forensic analysis software to create profiles of individuals along with mixtures of DNA representing groups of people from different genetic backgrounds.

Mixtures with lower genetic diversity were more likely to have a false positive result, or incorrectly link someone to a DNA mixture who wasn’t involved. Some groups that might have less genetic diversity include Indigenous, Latine, or Pacific Islander groups, researchers said.

That problem worsened when mixtures contained DNA from more people.

“The accuracy of DNA mixture analysis really varies by genetic ancestry,” Rohlfs said. “Groups with less diverse genetic variants are going to have higher false inclusion rates for DNA mixture analysis, and this gets worse when you have more contributors.”

Researchers said the study included the use of simulated genetic mixtures from “complex datasets,” so they cannot specifically say the forensic technique is less accurate for certain ancestry groups. Rohlfs added that traditional race and ethnicity labels are often overly broad and do not always accurately map genetic ancestry.

She noted this research also shows the challenges of conducting ethical genetic research, adding many of the studies her team analyzed did not necessarily practice informed consent when collecting people’s DNA, with some samples coming from incarcerated people.

This study, Rohlfs said, only included data from people where informed consent was verified, which limited their data pool.