A person’s blood alcohol content can be determined by testing a sample of the person’s blood. Compared to a breath test, a blood test is generally a more accurate method to determine a person’s blood alcohol concentration if the analysis is done correctly. However, blood alcohol analysis is a very complicated process and there are many factors related to blood testing that can cause the result to be unreliable.
During a blood alcohol test, blood is drawn from a person’s vein, usually from the arm, and then it is eventually analyzed using a very complicated process known as gas chromatography. If the blood test reveals the person’s blood alcohol concentration to be 0.08% or greater, that person is considered to be in violation of law (VC23152 (b)). The question is: Is the blood test result reliable?
The reliability of the blood test result is often an issue in the defense of a DUI case due to a number of factors including contamination of the blood sample itself during handling and storage of the sample, as well as the accuracy and reliability of the gas chromatography process.
To the untrained observer, the blood test result itself might be the end of the analysis. Many lawyers that pretend to defend persons accused of DUI will look at the blood test result and say: ―Yep, your blood test result is a 0.16%…that’s twice the legal limit; we better plead you guilty because nothing can be done to defend your case.
Even most prosecutors simply rely on the blood test result believing that the result is infallible, when in reality they know nothing about how the crime lab got to the result.
Remember back in math class in high school or college? If you turned your homework in with nothing but a list of answers, would you get a good grade on your homework? NO! Why? Because your math teacher wanted you to show your work; the teacher wanted to see HOW you got the answer! The same is true with blood testing, which is a scientific process. To know whether the result is accurate and reliable, the crime lab needs to show their work as to how they arrived at the result. I have said to many jurors: ―You have to be the math teacher and require the government to prove that the blood test result is accurate and reliable; the government has to show you their Work.
The first question with any blood test analysis is: How was the blood sample analysis performed? Meaning what type of method was used. Was the analysis completed using an Enzyme Assay test? Was the analysis done by Gas Chromatography (GC)? If Gas Chromatography was used, then what type of separation equipment was used as part of the process? If GC was used, then what type of analysis equipment was used as part of the process? The answers to all of these questions are very important as there are a number of potential problems associated with each method. As one can see from the previous discussion, science plays a significant role in the proper defense of a DUI case.
When defending a person accused of driving under the influence it is imperative that the lawyer has a deep understanding of the science behind blood alcohol testing and breath testing. Unfortunately, very few lawyers spend the time necessary to become a lawyer-scientist, and their clients suffer as a result. You cannot defend a DUI case if you do not know the science involved.