"A genetic witness": new ways police are using DNA to solve crime

The recent arrest in the 2012 Irasema Chavez murder case highlights how law enforcement investigators now use DNA beyond simple matching. When forensic evidence contains unknown DNA samples, police rely on newer technical methods to identify suspects. One method, DNA phenotyping, allows labs like Parabon Nanolabs to predict physical traits such as eye color, hair color, and ancestry from genetic data. This process generates a composite image that provides visual leads for investigators who otherwise have no description of a perpetrator.

While phenotyping offers a physical profile, it does not reveal age or non-genetic characteristics like tattoos or hairstyles. To bridge this gap, police also use genetic genealogy. This approach involves comparing crime scene DNA against massive genealogy databases where millions of individuals have shared their genetic information to learn about family history. By identifying distant relatives, detectives can map out family trees and eventually locate suspects who share the same genetic markers.

Texas Rangers and local police departments are increasingly relying on these tools to solve cold cases. With grant funding from the Department of Justice, agencies can access these private databases to pursue leads that were previously impossible to track. Services like the Genetic Witness Program on GEDmatch allow users to opt into law enforcement cooperation specifically for violent crime investigations and exonerations.

Despite the success in these investigations, the practice remains subject to strict oversight. Many states require that all traditional investigative avenues are exhausted before researchers turn to these advanced DNA techniques. Furthermore, genealogy platforms limit their collaboration to cases involving violent crimes or unidentified remains, ensuring that the use of genetic data remains targeted toward the most serious criminal matters.