Urine test kits issued by a state-run forensic lab in Santa Rosa were discovered to have been faulty, leading to potential false positives for alcohol intoxication in a small percentage of Sonoma County cases over nine years, and it’s unclear whether other counties were affected.
As the Chronicle reports, prosecutors announced this week that some criminal cases in Sonoma County may have relied on defective urine tests used to measure alcohol intoxication between 2016 and 2025. It's unclear whether the faulty kits were used in other California counties.
Assistant District Attorney Brian Staebell told the Chronicle that a state-run lab in Santa Rosa, the Bureau of Forensic Services, provided a list of 14 tests that were conducted using defective kits from supplier Andwin Scientific, though five were tied to investigations that did not result in charges. Most of the nine convictions using the faulty tests were primarily DUI cases. Per the Chronicle, prosecutors said they notified defense attorneys this week after identifying the affected convictions.
The faulty test kits reportedly contained an incorrect concentration of sodium fluoride, about 100 milligrams instead of the stated 750 milligrams, as the Chronicle reports. This could allow yeast and sugar to ferment, potentially producing inaccurate alcohol readings and “may result in an artificially elevated alcohol level in the sample,” said lab director Katina Repp in a January 28 letter.
Repp said inaccurate alcohol readings would likely occur only in samples with enough sugar and yeast to trigger fermentation, which can happen in people with certain health conditions or infections, as the Chronicle reports. She said the lab stopped shipping the affected kits and notified the supplier after discovering the issue in August 2025, noting that kits distributed since September should contain the correct concentration.
“It is impossible to assess whether samples taken during investigations of criminal matters, including but not limited to DUI investigations or sexual assault investigations, were properly preserved,” Repp wrote, per the Chronicle.
Sonoma County Public Defender Brian Morris said his office will evaluate each of its cases involving potentially faulty test kits.
“When the government’s own lab acknowledges that faulty testing kits may have artificially inflated alcohol levels over a nine-year period, it raises serious concerns about the reliability of their forensic testing, internal controls, and safeguards,” Morris said in an email to the Chronicle. “It also puts the integrity of convictions based on DOJ evidence in serious doubt.”
In a separate case, the Guardian reported last year that thousands of drug tests used in California prisons in 2024 may have produced false opiate positives after Quest Diagnostics changed a testing reagent, with monthly positive rates jumping from about 6% to 7% to as high as 20%, according to prison medical records.
Image: Lothar Drechsel/Getty Images
