Illustration by Alex Castro / The Verge

The San Francisco Police Department includes DNA collected from rape kits in the database it uses to identify crime suspects, District Attorney Chesa Boudin said on Monday. The practice likely is illegal under the California Constitution, Boudin told The Washington Post.

The district attorney’s office discovered the practice when reviewing the case of a woman arrested for property crime. She was identified as a suspect based on a DNA sample collected during a rape investigation in 2016. Searches that include genetic information from rape investigations are done regularly, the crime lab confirmed to Boudin.

Use of this type of data could violate the California Constitution, which requires property be returned to victims when it’s no longer needed as evidence, and the Fourth Amendment of the United States Constitution, which protects against unreasonable search and seizures, Boudin says.

This type of practice could also discourage victims of sexual violence from coming forward or agreeing to DNA testing as part of a rape kit. It “does real damage to the trust that we need from folks who survived sexual assault,” Boudin said. He said the district attorney’s office will not use this type of evidence, and state and local policymakers said they’re looking into legislation to make the practice illegal.

DNA evidence not originally intended for the identification of crime suspects increasingly leaks into criminal investigations. Law enforcement officers sometimes use genetic information from consumer genealogy companies to identify suspects, a practice that took off and raised privacy concerns after it was used to identify the suspected Golden State Killer in 2018. Two states, Maryland and Montana, passed laws last year limiting use of the technique by law enforcement.

Adding a person’s DNA to databases doesn’t just link law enforcement to that particular person, either — it also could connect them to relatives. One analysis found that experts could identify around 60 percent of people with European ancestry in the US from a database of around 1.3 million people.