The Orange County Crime Lab has found more errors in its blood-alcohol testing and plans to request a state audit to review its procedures and case standards.
The discovery comes a couple of weeks after the lab acknowledged inaccurate blood alcohol test results in 2,200 driving-under-the-influence cases filed by prosecutors this year.
Prosecutors sent letters this month to people charged with driving under the influence, including 900 whose cases resulted in convictions. The letters advised them that their cases were among those with miscalculations.
Crime lab officials said the "human error" occurred over nearly five months and led to mistakes in the forensic examination of blood alcohol content. But they insist the miscalculations affect only about 200 cases. As few as 20 people could see their blood alcohol test levels drop below 0.08%, California's legal definition of DUI impairment.
Orange County Crime Lab Director Bruce Houlihan had previously told The Times that the lab tests each blood sample twice using two machines and then averages the results.
One of the machines was off by 0.003 percentage points, he said.
In a statement released Thursday, Orange County Sheriff's officials said the lab discovered problems with the second machine, which resulted in a calibration error of .001 between December 2012 and May 2013.
Authorities said that the blood-alcohol results were underestimated in at least 100 cases and will be corrected. In nine of those cases, the level will change from .07 to .08, which would result in those drivers testing above the legal blood-alcohol content limit for driving, sheriff's officials said.
The second error was found after an internal audit.
"I am confident that the Orange County Crime Lab is taking the necessary steps to insure that these clerical errors do not occur in the future," Orange County Sheriff Sandra Hutchens said in a statement.
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