Watch any episode of “CSI,” and a character will use forensic DNA profiling to identify a criminal. A new study from San Francisco State University suggests that these forensic profiles may indirectly reveal medical information — perhaps even those of crime victims — contrary to what the legal field has believed for nearly 30 years. The findings could have ethical and legal implications.

“The central assumption when choosing those [forensic] markers was that there wouldn’t be any information about the individuals whatsoever aside from identification. Our paper challenges that assumption,” said first author Mayra Bañuelos (B.S., ’19), who started working on the project as a San Francisco State undergraduate and is now a Ph.D. student at Brown University.

Law enforcement uses the Combined DNA Index System (CODIS), a system organizing criminal justice DNA databases that uses specific genetic markers to identify individuals. Crime labs from national, state and local levels contribute to these databases and provide profiles from samples collected from crime scene evidence, convicted offenders, felony arrestees, missing persons and more. Law officials can use the database to try to match samples found in an investigation to profiles already stored in the database.

CODIS profiles consist of an individual’s genetic variants as a set of short tandem repeats (STRs), sequences of DNA that repeat at various frequencies among individuals. Since the ’90s, 20 STRs have been chosen for forensic CODIS profiling specifically because it was believed they did not relay medical information. If these profiles contained any trait information, then there could be issues about medical privacy.

“But that assumption hasn’t had much investigation in a long time, and we know a lot more about the genome now than we did back then,” explained SF State Associate Professor of Biology Rori Rohlfs, who led this project.

The assumption that only criminals are sampled is also not completely accurate. “It actually also includes victims of crime and people that may have been at crime scenes. You have these huge databases including a lot of people that are not necessarily criminals,” Bañuelos said. “I believe also that accessibility to these databases varies a lot according to a jurisdiction.”

The researchers explained that other papers have found associations between other (non-CODIS) STRs and disease or gene expression. With that in mind, the SF State team wanted to understand the relationship between the CODIS STR markers and gene expression.

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