California Drunk Driving – BAC Tests


Simply driving a vehicle in San Diego – or anywhere in California — legally and automatically implies consent to submit to a test for alcohol or drug content if suspected of drunk driving by a San Diego Police Officer, or any other law enforcement personnel.

California State Law references to “Blood Alcohol Content”, or BAC, refer the number of grams of alcohol present per 100 millimeters of blood in a DUI suspect’s system. A BAC of 0.10% would mean that the person has 1/10 of a gram of alcohol per every 100 millimeters of blood in their body. It is easy to see how a San Diego driver can all-too-easily be mistakenly accused of driving drunk; the legal limit of 0.08% represents a very small percentage of alcohol in the blood.

When chemical evidence is admitted for use in a San Diego drunk driving case, there are typically several methods for challenging the accuracy of a breath test. Blood testing consists of taking a blood sample and directly measuring the alcohol and/or prohibited drugs and/or their metabolites.

If you have been arrested for drunk driving in San Diego or other state jurisdictions, or have consented to a breath test, you are permitted to have a second blood test conducted by an independent source, at your expense.


While blood tests are the most reliable method of testing for BAC, they are not infallible. Typically, blood samples are drawn by hospital staff. (San Diego Police Officers do not have sufficient phlebotomy training to legally draw your blood on suspicion of the presence of alcohol and / or drugs.)

The fact is the methods used to draw blood can have a significant impact on test results and therefore on admissibility of this evidence in your San Diego drunk driving case. Medical personnel are required to have necessary credentials and follow precise procedures; otherwise, the test results may be subject to challenge. Contaminated samples or flawed procedures can also influence and/or erroneously inflate BAC results.

Provided below is a partial list of sources and examples of defense(s) related to blood tests that may be relevant to your San Diego Drunk Driving case:

HIPAA: The Health Insurance Portability and Accountability Act of 1996 is an evolving piece of legislation and area of healthcare law. Basically, any entity that has access to your medical records or produces any patient medical information (such as test results), must adhere to a strict set of complex guidelines in order to protect patient privacy. Noncompliance with HIPAA regulations by a healthcare provider can influence the admissibility of your blood test results and likewise the outcome of your case.

Yeast: If introduced into the blood sample, can produce falsely high BAC readings. Yeast consumes blood sugars. The byproduct is alcohol – indistinguishable from alcohol whose source is an alcoholic beverage.

Non-sterile tube: The top of the blood test tube has been contaminated or has not been properly sterilized.

Administrative Errors: The lab or hospital has incorrectly identified your sample and your test results are from someone else’s blood. This can be definitively verified through a DNA test.

Alcohol Swab: If the site of the needle puncture on your arm was first sterilized with any substance containing alcohol, this alcohol can be transferred to the needle and ultimately into the blood sample and generate erroneously high BAC results.

Defective Vacuum: Tubes used to collect blood contain a vacuum that helps deposit blood into the tube. If this vacuum is damaged or does not function properly, contaminants can be introduced that could influence test results.

Breath Tests

A breath test measures only alcohol and is more error prone. Equations are used to gauge the relative amount of alcohol contained in a sample of deep lung (alveolar) air and law enforcement then has to calculate the amount of blood alcohol that should be present. Testing alveolar air has its problems, in that the sample does not necessarily remain constant. Temperature and breath patterns also affect the content of any given breath sample. Many common substances can register as alcohol, skewing test results and calling into question key evidence in your San Diego drunk driving case.

There are several breath test machines (commonly referred to as a breathalyzers) available on the market. They are manufactured by private companies and sold to law enforcement agencies. These varying devices come with unique characteristics and requirements for proper use and care. The improper use, testing and/or maintenance of these various devices can play a significant role in your defense. It follows that it is vitally important to select an attorney for your San Diego drunk driving case with expert knowledge of these machines.

Even the most advanced breathalyzers (e.g., the Intoxilyzer) can have problems. It uses infrared spectrometry to measure the amount of alcohol in a breath sample. A quartz lamp inside the machine radiates infrared energy through the sample. The amount of energy that makes it through the sample (i.e., not absorbed by alcohol) is then measured. The greater the amount of alcohol present in the sample, the greater the absorption. To deliver results admissible in court, however, the breath testing device must have been properly maintained and operated. Even when functioning properly, this device has a modest but inherent margin of error that can affect the outcome of your San Diego drunk driving case.


Even if you’ve failed a chemical test, there are means for challenging the results and having a successful outcome for your San Diego drunk driving case. A skilled and experienced attorney will professionally assess how these test results may be successfully defended against or thrown out altogether.

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