When someone is charged with DUI in California, prosecutors often treat blood test results as irrefutable proof of guilt. But those numbers don’t always tell the full story. Behind every test is a human process—subject to contamination, mislabeling, improper storage, and flawed interpretation. At Chambers & Ball, we’ve successfully challenged DUI blood test results by uncovering the errors and shortcuts that laboratories rarely admit.
Why Blood Tests Are Used in DUI Cases
California law enforcement frequently relies on blood alcohol concentration (BAC) to determine impairment. Under Vehicle Code 23152(b), a BAC of 0.08% or higher typically constitutes a DUI, and even lower levels can be used as evidence if combined with signs of poor driving or judgment.
Unlike breath tests, which measure alcohol in the lungs, blood tests directly measure alcohol in the bloodstream—making them appear more reliable. However, that reliability depends entirely on the procedures used to collect, store, and test the sample.
How Blood Testing Can Go Wrong
Blood tests are only as accurate as the chain of custody and lab conditions behind them. Common errors include:
- Improper Collection: Blood must be drawn using the correct preservatives (like sodium fluoride). Without them, the sample can ferment, producing artificially high BAC results.
- Contamination: If the draw site isn’t properly sterilized or equipment is reused, bacteria can alter the chemistry of the sample.
- Mislabeled Samples: In busy crime labs, cross-contamination and sample mix-ups are not uncommon.
- Improper Storage: Blood samples must be refrigerated and handled under strict time limits. Delays or temperature fluctuations can skew results.
- Faulty Testing Equipment: Lab instruments require regular calibration and maintenance. Even small deviations can produce inaccurate readings.
The Role of Human Error and Automation
Most blood testing in California is performed by technicians following automated processes. But “automation” doesn’t mean infallibility. Software glitches, misentered data, or lapses in record-keeping can easily lead to inaccurate reports. Prosecutors rarely highlight these weaknesses—but an experienced defense attorney knows where to look.
How Chambers & Ball Challenges Blood Test Evidence
At Chambers & Ball, we approach blood evidence like a scientific investigation. Our defense strategies often include:
- Requesting Full Lab Documentation: We obtain maintenance logs, technician credentials, and calibration records to identify irregularities.
- Reviewing Chain of Custody: Any gap in documentation between collection and testing can render results unreliable.
- Consulting Independent Experts: We work with forensic toxicologists to reanalyze samples or interpret raw chromatograph data.
- Highlighting Procedural Violations: If the test violated Title 17 of the California Code of Regulations (which governs DUI testing standards), the evidence may be suppressed.
- Questioning BAC Correlation: Even if alcohol was present, we challenge whether the result accurately reflected impairment at the time of driving.
Through these methods, we’ve helped clients achieve charge reductions, dismissals, and acquittals in cases where prosecutors assumed the science was settled.
Why This Defense Matters
A DUI blood test result is often the prosecution’s strongest piece of evidence—but also their most vulnerable one. When juries learn how easily errors can occur and how little oversight some labs maintain, they begin to question the state’s entire case.
Even a difference of 0.01% BAC can change the outcome—transforming a felony into a misdemeanor or avoiding conviction entirely.
Protect Your Rights and Your License
If you’ve been charged with DUI based on a blood test, don’t assume the results are accurate or final. The truth often lies in the fine print of the lab reports.
Call 714-760-4088 today to schedule a confidential consultation with Chambers & Ball. We’ll review your blood test documentation, identify weaknesses in the prosecution’s case, and fight to protect your record, your license, and your future.
