Researchers reveal the complexities and limitations of forensic DNA analysis, especially when dealing with DNA mixtures from genetically similar groups.
The study, using simulated genetic mixtures, indicates that such groups are more prone to false positives, raising ethical concerns about the use of DNA evidence in criminal investigations.
Forensic DNA Challenges
A swab of DNA from a door handle or drinking glass isn’t always a foolproof way to determine who committed a crime.
Researchers at the University of Oregon, writing in the journal iScience, found that forensic DNA analysis becomes less reliable when dealing with DNA mixtures from groups with low genetic diversity. In such cases, the technique is more likely to wrongly identify an innocent person as being present at the scene — a mistake with potentially life-altering consequences.
Advances and Limitations in DNA Analysis Techniques
Modern DNA analysis is highly sensitive, capable of detecting even tiny traces of genetic material left behind by skin cells. This allows forensic scientists to link DNA to specific individuals. However, this sensitivity comes with a challenge: DNA samples often contain genetic material from multiple people, such as everyone who recently touched the same door handle. This can make it harder to pinpoint whose DNA is relevant to the investigation.
By looking at the variation of certain genetic markers in the sample and comparing it to the suspect’s DNA, researchers can quantify the strength of the evidence linking a particular person to the mixture.
The Impact of Genetic Ancestry on DNA Analysis Accuracy
DNA mixture analysis can be powerful when used correctly, but it’s crucial to understand the technique’s limitations and when it should be wielded with particular caution, said Rori Rohlfs, a data scientist at the University of Oregon who led the work alongside a group of undergraduate researchers from San Francisco State University.
Rohlfs and her team wanted to see how the accuracy of that approach is affected by people’s genetic ancestry. They combed through previously published genetic databases to get data on the frequency of certain genetic variants for groups of people with different genetic ancestry. Then, they used forensic analysis software to simulate profiles of individuals, as well as mixtures of DNA representing groups of people from different genetic backgrounds.
In mixtures with lower genetic diversity, the team found the technique was more likely to yield a false positive; that is, to incorrectly link someone to the mixture who wasn’t actually involved. And the problem worsened when the mixture 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.”
Ethical Considerations in Genetic Research
The study involved simulated genetic mixtures generated from complex datasets, so the researchers can’t specifically say that the technique is less accurate for certain genetic ancestry groups. Plus, traditional race and ethnicity labels are often overly broad and don’t always accurately map to genetic ancestry, Rohlfs said.
“The accuracy of DNA mixture analysis really varies by genetic ancestry. 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.”
Rori Rohlfs, UO data scientist
However, some examples of groups that might have less genetic diversity include certain Indigenous, Latine or Pacific Islander groups.
The research also reflects the challenges of doing ethical genetic research, Rohlfs said. Many of the studies her team looked to for data did not necessarily practice informed consent when collecting people’s DNA, sometimes getting samples from incarcerated people. The research team opted to only include data from subjects where informed consent could be verified, somewhat limiting their data pool.
Rohlfs is currently building up her lab at the UO, and she hopes to continue investigating the accuracy of other emerging forensic DNA analysis techniques.
Reference: “Decreased accuracy of forensic DNA mixture analysis for groups with lower genetic diversity” by Maria Flores, Evan Ho, Cara Ly, Niquo Ceberio, Miguel Guardado, Kamillah Felix, Hannah Mariko Thorner, Matt Paunovich, Chris Godek, Carina Kalaydjian and Rori V. Rohlfs, 28 September 2024, iScience.
DOI: 10.1016/j.isci.2024.111067
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1 Comment
One child in a family of 4 children has a different DNA and supposedly a different father. How? No chance of mother having affair. Supposed father has never been in the same state as mother. Help!!!!!