Blood Test Evidence in DWI Cases
DWI Attorneys in North Carolina Challenging Blood Test Evidence
While the breath test is supposed to measure Blood Alcohol Content (BAC), it doesn’t give the same reading as a blood test. In reality, your breath test could be substantially different from your blood test. But why? Well, it’s because the two tests are actually measuring different things. The alcohol content of the alveolar air is being measured in a breath test. The standard partition ratio of 2,100 to 1 is then applied to estimate your blood alcohol level. But a blood test will measure the percentage of alcohol in whole blood. As a result, the two tests could vary, assuming your partition ratio is not 2,100:1. The state of North Carolina typically relies on blood tests in DWI charges involving accidents. This is because the driver is often unable to take a breath test.
If you have been arrested for DWI, call us at (800) 930-0397 for an initial free consultation.
Do Blood Tests Yield Perfect Results?
Hardly. The car wreck scenario itself can throw off the test results. The basic factors of the wreck should be investigated as part of your defense. Folks are surprised to learn about the number of errors that can occur. Finding blood alcohol content from blood that may have been drawn for other purposes can create problems. If the test is from blood that was drawn in the emergency room, and the nurse used an alcohol antiseptic to sterilize the skin before inserting the needle, the blood could be contaminated by residual alcohol on the skin. Also, in many cases, ER doctors request that blood samples be centrifuged for immediate analysis and treatment. This results in a concentrated blood plasma, and if this blood plasma is then tested for alcohol, it will have a different amount of alcohol compared to the whole blood taken from the same person at the same time.
In addition, what if you lose a significant amount of blood because of injury? Your blood alcohol content will be falsely high. Since there’s less blood in your system to absorb the alcohol, it’s concentrated in the blood that’s left in your body. Since many DWIs involving wrecks happen shortly after the driver stopped drinking, in many cases the alcohol is still being absorbed after the accident. If you receive a blood test after losing at least two quarts of blood, your blood results could be off by 20 percent or more.
Are There Any Other Factors that Might Skew Blood Test Results?
Absolutely. Anemia can make the test inaccurate. Anemic people have a shortage of red blood cells. This leaves fewer cells in whole blood and more plasma, creating a higher ratio of alcohol to red blood cells than would otherwise be the case. This is especially relevant for women who are anemic and experiencing their period. The percentage of alcohol in their brain tissue could be lower than the reading on the machine.
Finally, it’s important to determine when the blood was drawn for the test. It can be drawn after paramedics have already started administering other drugs or foreign substances into the body for the purposes of treating an injured driver. Whether it’s blood plasma or amphetamines to stimulate the heart and lungs, it can skew the test results by changing your absorption rate for alcohol. It can also affect your rate for dispelling alcohol. If your heart rate has been accelerated, the alveoli will be dispelling ethanol at a greater rate even if your actual blood alcohol content is below .08.
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