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San Jose DUI Defense Strategy Lawyer

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How to Defend Against a DUI Charge in Santa Clara County

There are many defenses to a charge of driving under the influence, some of which are technical and/or scientific in nature. This is why "discovery" and the collection of evidence is so important in DUI cases and why a good lawyer will review every bit of information, from the nature of the stop, to the manner in which the field sobriety tests were conducted, whether the PAS device was used properly, and whether the blood sample was taken and stored in a medically approved manner.

If you have questions regarding what defense may be available in your DUI case, contact our law office in San Jose.

Possible Defenses To DUI Charges In California

Defenses to a DUI charge include:

  • Rising blood alcohol or retrograde extrapolation: It is illegal to be driving while under the impairment of alcohol. The per se law in California makes it illegal to be driving with a blood-alcohol content of .08 percent or more. However, when blood is drawn, the suspect is already arrested and in the custody of police.

When you consume alcohol the body absorbs it into the blood system, which is your blood-alcohol content. As the alcohol continues to be absorbed through the stomach and lower intestine, the blood-alcohol content will continue to rise until it hits a peak at some point. The rate of absorption has many varying factors such as a person's metabolic rate, how fast alcohol was consumed, whether it was consumed with food and the type of alcohol consumed.

It may be that when your blood is taken you are still in a "rising" state, where the absorption process is not complete. You can then "extrapolate back" to determine a lower blood-alcohol content at the time of driving. This is called retrograde extrapolation and a rising blood-alcohol defense.

  • Errors in blood collection and violations of Title 17: This analysis requires an examination of whether the blood was taken in a medically approved manner, the type of blood taken (arterial versus venous), how the blood was stored and whether measures were taken to prevent degradation of the sample, including the anti-coagulate used. Further analysis should be made into the qualification of the phlebotomist, chain of custody of the blood vial and calibration of the devices used to ascertain the alcohol content.
  • Necessity defense: This is a somewhat nuanced defense, but a valid one. In this scenario, the driver is forced into a DUI in order to avoid imminent harm to life or property. In this case, the driver knowingly drove while under the influence but did so to avoid an imminent threat of bodily harm. For example, a person is being violently attacked by an assailant and the only way to escape is to drive away. The necessity defense would apply.
  • No evidence of driving: The prosecutor must prove you were driving while intoxicated. This includes cases where the suspect is found in the vehicle, but no observations of driving were made. It is important to note whether the engine hood was warm, whether the keys were in the ignition and the physical location of the suspect (was he in the driver's seat or asleep in the back seat?) when the police made contact.
  • Impairment defense: A prosecutor may have to show that the driver was impaired, which affected his or her ability to drive. However, often no "bad driving" was observed or cannot otherwise be properly articulated. Further, errors in field sobriety tests are common place and can be attacked at trial. Police officers are not experts in the instruction and observation of field sobriety tests and their credibility can be impeached by a good attorney.


Field sobriety tests were designed with failure in mind. Most certainly the arresting officer will testify that you failed the FSTs and will attempt to explain why. A good lawyer knows how to rebut these subjective opinions of the cop and impeach his or her credibility by cross examination. Police officers rarely instruct FSTs in the manner required by the NHTSA Standardized Field Sobriety Instructions Manual, making any observations of those FSTs questionable.

Additionally, breath test samples can be easily corrupted and give false readings. This can happen by improper calibration and maintenance by the police, or simple belching by the suspect.


A police officer is required to wait and observe 15 to 20 minutes before administering the breath test. This is to ensure that the subject of the PAS test did not regurgitate, belch, vomit or even take a last minute drink of alcohol immediately before giving a breath sample.

  • Suppression of evidence: Evidence that was collected in violation of law should always be moved to suppress and excluded from evidence. Examples of this are:
    • Lack of probable cause for the stop; if the prosecution cannot prove probable cause for the stop in the first place, any evidence collected as a result of the stop, including observations and test results should be excluded
    • Blood collected in violation of proper medical procedures, including qualifications of the person who took the blood
    • Faulty calibration and maintenance of PAS device
    • Break in the chain of custody of blood or urine samples
    • Improper DUI checkpoints
    • Errors in field sobriety tests, including order and timing of tests
    • Lack of or defective implied consent admonishment

Find Out More About Your Defenses To DUI Charges

The defenses available to you will depend on the unique circumstances in your case. Contact your relentless Santa Clara County DUI defense attorney at the Law Office of Erik Steven Johnson at 408-246-3004 to find out what defenses are available to you, so we can get to work defending your rights.

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