Study Highlights Limitations in Forensic DNA Analysis Involving Lower Genetic Diversity Groups
by Jo Ellen Not
A University of Oregon study, “Decreased accuracy of forensic DNA mixture analysis for groups with lower genetic diversity” published in Volume 27, Issue 11, 111067 of iScience in November 2024 by researchers at the University of Oregon, discusses the significant limitations in forensic DNA analysis when trying to interpret DNA mixtures that contain samples from groups of people with low genetic diversity.
While DNA analysis has revolutionized forensic science, it is crucial to recognize its limitations and potential for misinterpretation. The study found that DNA mixture analysis, a technique used to identify individuals from a mixture of DNA profiles, that, for example, could be found on a door handle of a crime scene is more likely to produce false positive results in populations with lower genetic diversity. This means that an innocent person could be wrongly implicated in a crime due to the limitations of the technique.
Who is an individual from a lower genetic diversity group? A lower genetic diversity group is characterized by living in isolated or protected colonies that do not mingle or mix with other groups. In the animal world, low genetic diversity often occurs due to habitat loss, so individuals of a species are forced to live in more compacted groups with less introduction of new members. In the human world, living apart, practicing social isolation, and marrying within the group leads to loss of genetic diversity. In small populations, the choice of mates is limited. Over time, individuals will all become related, thus reducing variations in their gene pool. This is inbreeding and is characterized by having identical copies of genes.
Led by data scientist Rori Rohlfs, the research team simulated genetic mixtures using diverse ancestry databases. They discovered that DNA mixtures from groups with less genetic diversity—such as certain Indigenous, Latino, or Pacific Islander populations—were more prone to false inclusions or false positive rates. This risk further increased with the complexity of a DNA mixture involving multiple contributors. The researchers emphasized the importance of understanding the genetic ancestry of individuals involved in a case.
The study also highlights ethical concerns surrounding the use of genetic data in forensic science. Many genetic databases used in previous research efforts were collected without informed consent, raising questions about privacy and the potential for misuse of personal genetic information. In several cases, the genetic data bases studied were from incarcerated individuals. To address these concerns, the University of Oregon team used data verified for informed consent, but this, of course, limited the sample size.
The findings of this study have implications for the criminal justice system. It is essential for forensic scientists, legal professionals, and judges to be aware of the limitations of DNA analysis and to interpret the results with caution, especially in cases involving complex DNA mixtures and individuals from underrepresented populations with less genetic diversity.
Sources: Frontiers for Young Mind; University of Oregon News
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