In a significant case out of Oceano Dunes California (SLO County), California DUI Attorney Matthew Ruff leveraged the scientific principle of retrograde extrapolation to successfully challenge his client’s breath test results and achieve a dismissal of the license suspension. This victory hinged on proving the client was still in the “absorptive phase” of alcohol consumption, meaning his blood alcohol concentration (BAC) at the time of driving was below the legal limit of 0.08%, despite higher readings later at the police station.
The Facts of the Case
- 15:08: Client pulled over by law enforcement.
- 15:16: Client arrested after displaying objective signs of intoxication (odor of alcohol, bloodshot/watery eyes).
- 15:40: First breath test administered, result: 0.089% BAC.
- 15:43: Second breath test administered, result: 0.091% BAC.
The “Rising BAC” Defense Strategy
The core of the defense was to exploit the time gap between the initial stop (15:08) and the breath tests (starting at 15:40). California law prohibits driving at or above a 0.08% BAC, but if the tests are taken while alcohol levels are still rising, the results may not reflect the actual level at the time of driving.
Attorney Ruff used a linear extrapolation (also known as retrograde extrapolation) to estimate the client’s BAC at the moment he was pulled over.
- Calculate the Rate of Increase: The client’s BAC increased from 0.089% to 0.091% over a 3-minute interval (15:40 to 15:43). This rapid increase was key evidence that the client was in the absorptive phase.
- Project Backward: Mr. Ruff demonstrated that by projecting this rate backward in time to 15:08 (32 minutes before the first test), the client’s BAC would have been below 0.08%.
- Calculation: The increase was 0.002% in 3 minutes. Over 32 minutes, the projected drop in BAC was approximately 0.021%.
- Result: 0.089% (at 15:40) – 0.021% = ~0.068% at the time of driving.
This expert analysis showed that the client was likely innocent of the core DUI charge (driving with 0.08% or more BAC).
The Outcome: License Suspension Set Aside
By highlighting the discrepancy between the time of driving and the time of testing, and providing a scientifically sound estimate of a sub-0.08% BAC, Matthew Ruff successfully challenged the validity of the evidence at the DMV hearing. In addition, Matthew showed other “evidence” relied upon by the police officer was not reliable, such as the conclusions drawn from a horizontal gaze nystagmus (HGN) test.
The DMV hearing officer agreed, and the administrative per se (APS) license suspension order was set aside, and the arrest was removed from the client’s DMV record. This outcome is considered a total victory, protecting the client’s driving privileges and avoiding severe penalties.
It is also noteworthy that Matthew got the criminal charges of VC 23152a and VC 23152b dismissed in Court following negotiations with the DA, thereby avoiding a trial in Court. The client, a commercial driver, was elated. The consequences he was facing was a lifetime disqualification of his commercial license.
Would you like to know more about how Matthew Ruff has used challenges to police observation periods or breath machine accuracy to win other cases? Visit Matthew’s website Best DUI Defense.
Matthew Ruff is a top-rated criminal defense and DUI attorney in Southern California with over 30 years of experience. He specializes exclusively in DUI and criminal law, having handled over 4,000 cases including standard DUIs, high BAC cases, and underage offenses.
