Los Angeles DUI - Whole Blood vs. Serum Analysis

Whenever a driving is arrested for driving under the influence of drugs or alcohol, he or she will be given the opportunity to take either a breath or blood chemical test. If the driver chooses the blood test, a sample of the driver’s blood will be withdrawn and will be sent to a laboratory for analysis. Unlike the breath test, the results of the blood test would not be known immediately and the defendant typically would not learn what his or her BAC was until they receive the lab results as part of the discovery packet provided by either the prosecution or the Department of Motor Vehicles. While the blood test is generally considered to be the more accurate form of chemical testing, there may be issues regarding how the blood sample was tested that can be relevant in determining whether or not a driver’s BAC was above the 0.08 percent threshold.

Most blood samples in DUI cases are analyzed as a whole blood sample. This means that the entire blood sample is analyzed and is not separated. Most blood samples that are analyzed for medical purposes will conduct tests on blood serum. Blood serum is the clear, yellowish fluid that is obtained after blood is separated into liquid and solid components by spinning the sample in a centrifuge device. There is a third method of analyzing blood which involves precipitating proteins from the sample and then using a centrifuge to separate the sample. This produces a liquid referred to as a “supernatant” which can then be analyzed for blood alcohol content.

It is important to know what type of analysis was conducted on the blood sample in a DUI case. Studies have shown that analyses conducted on serum or supernatant will result in higher BAC levels than analyses conducted on whole blood samples. The blood alcohol level in a serum analysis is approximately 11 percent higher than the results of a whole blood analysis. Supernatant analyses yield results that are approximately 5 percent higher than whole blood. The reason that serum BAC levels are higher is that serum contains more water than whole blood. Because alcohol has an affinity to water and is chemically attracted to it, serum samples will produce higher BAC results.

This difference can be critical for defendants whose BAC is at or close to 0.08 percent. For example, a defendant whose blood test result on a serum analysis had results of 0.08 or 0.09 percent may have results of 0.07 on a whole blood analysis. If this were the case, the defendant may not be criminally liable for driving with a blood alcohol content of 0.08 percent or higher in violation of California Vehicle Code Section 23152(b) VC.

While it is usually the case that whole blood analysis is completed on a defendant’s blood sample in a DUI case, there may be situations where serum analysis has been completed. This may be the case where the defendant was brought to a hospital or medical facility for treatment following a traffic collision and his or her blood sample was collected and analyzed by medical professionals.

Although it is the general practice to analyze whole blood samples in non-medical cases, scientists agree that serum analysis provides a more accurate result than whole sample analysis and is the preferred method. This is because whole sample analysis may vary due to the fact that alcohol is not uniformly distributed in a whole blood sample.

Where the defendant has provided a blood sample, he or she can request a blood split order that would allow a portion of the sample to be retested at an independent laboratory. In many cases, the results of the retest may reveal a significantly lower blood alcohol content. If you have been stopped and arrested for a DUI offense and have provided a blood sample for analysis, it is critical that you speak with a Los Angeles DUI Attorney as soon as possible. As a former Deputy District Attorney with over 14 years of prosecutorial experience, Lawyer Michael Kraut works closely with top experts and independent laboratories to ensure his clients have access to the most comprehensive defense possible. For more information about whole blood and serum analysis in Los Angeles DUI cases, and to schedule your free consultation, contact Michael Kraut at the Kraut Criminal & DUI Lawyers located at 6255 Sunset Boulevard, Suite 1520, Los Angeles, CA 90028. Mr. Kraut can be reached 24/7 at 888-334-6344 or 323-464-6453.