Faulty DNA test kits were used in thousands of L.A. County criminal cases, authorities say
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In August, a manufacturer of DNA testing kits sent a letter to the Los Angeles County Sheriff’s Department warning officials to stop using certain test kits that had proved prone to giving incomplete results.
The letter eventually landed in front of a civilian employee at the department’s Scientific Services Bureau — but the employee didn’t throw the kits out or send them back, sheriff’s officials said Wednesday.
Instead, the department kept using the faulty kits for another six months, testing thousands of samples from an array of criminal cases and investigations.
It wasn’t until Monday that a Scientific Services Bureau supervisor discovered the testing-kit company’s notice and officials realized what had happened.
Now, the department has opened an internal administrative investigation into the incident as officials face the daunting task of retesting 4,000 samples and figuring out how much the flawed kits may have affected criminal cases. In some cases, existing samples may be too small to retest, the department said.
The wife of a slain fire captain was arrested in Mexico over the weekend and pleaded not guilty to a charge of first-degree murder.
“We take the integrity of our criminal investigations and the reliability of our forensic testing very seriously,” Sheriff Robert Luna said in a news release Wednesday afternoon. “The Sheriff’s Department is working diligently to assess the impact and to prevent such situations from occurring again.”
The department did not provide a copy of the company’s letter and declined to name the company. Sheriff’s officials said the civilian employee involved in the incident is no longer with the department but did not specify why the person left or when.
In total, the department used the defective kits for eight months, from July 2024 through February 2025.
“Based on the information provided by the DNA testing kit manufacturer,” the department said, “the use of the affected kits may have led to incomplete or suboptimal results but is not likely to have falsely identified any individual.”
Los Angeles County Dist. Atty. Nathan Hochman said his office had begun working with the Sheriff’s Department to assess the scope of the problem and make sure those involved — including defendants, victims and the public — are kept informed.
“We will follow the facts in whichever direction they take us on any individual case and make decisions that are in full accordance with the law on how to remedy any particular situation that requires such remediation,” he wrote in a statement. “Ensuring the integrity of the criminal justice process to build and maintain trust in its outcomes is paramount as we go forward.”
Brooke Longuevan, president of the public defenders union, called the situation “deeply concerning.”
“This failure will undoubtedly delay criminal cases, leaving our clients in custody waiting even longer for their trials to move forward,” she said. “Serious oversights like this not only jeopardize the integrity of individual cases but also sow public distrust in the criminal legal system and call into question the efficacy and accuracy of criminal investigations.”
