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Sacramento, California – A lab testing error led to thousands of California state prison inmates receiving false positive results for opioid use in 2024, raising serious concerns that many may have been unfairly denied parole based on inaccurate drug records.
Roughly 6,000 drug screenings conducted between April and July 2024 returned false positives due to a chemical reagent error by Quest Diagnostics, the private lab contracted to perform testing for California’s 31 state prisons. The affected tests, used during drug treatment programs, were logged in inmates’ medical records and often factored into parole hearing decisions, despite not being intended for punitive use.
“This was a clinical test, but its consequences are potentially life-altering,” said Natasha Baker, an attorney with the nonprofit advocacy group UnCommon Law. “You have the parole board making life-or-death decisions based on a drug screen that may be wrong.”
UnCommon Law uncovered the issue through public records requests, which showed a sudden spike in positive drug results during the three-month period. Opiate positivity rates typically hover around 6% in the prison system, but in June 2024, they surged to 20%. The spike triggered internal reviews, eventually revealing that a temporary reagent Quest Diagnostics used had inflated the presumptive positives rate.
In a statement, Quest Diagnostics said that the FDA approved the replacement reagent, but admitted it may have led to more false positives. The company emphasized that the results were only meant for clinical use and noted that confirmatory testing was available — but often not requested.
According to UnCommon Law, at least 15 California prisons logged more than 200 false positives each. More than 20% of tests may have been inaccurate at Corcoran State Prison. A memo from California Correctional Health Care Services (CCHCS) confirms it is in the process of notifying affected inmates and updating their electronic health records. The Board of Parole Hearings was also briefed on the incident.
However, Baker said how many parole decisions have already been influenced remains unclear. “Someone could go to a parole hearing in 2028 and be blindsided by a 2024 drug test that was never confirmed and shouldn’t have been considered,” she said.
UnCommon Law is calling for all test results from the affected period to be excluded from parole decisions. “All of those tests should be wiped because they were tainted,” Baker said. “That’s the only fair way to move forward.”
