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December 20, 2013

How Reliable are Tests to Gauge Alcohol or Drug Levels?

Filed under: DUI,DWI — admin @ 3:56 pm


There have been quite a few stories in the news as of late describing DUI cases where the judge has had to dismiss evidence from field sobriety, urine, blood, and breathalyzer tests due to their unreliability. Here are some of the myths surrounding the common methods of measuring sobriety, and why it is better to have a DUI attorney on your side if you are facing DUI charges.

Field sobriety tests have always been controversial because they rely on the opinions of the officer giving the test, who may not consider any medical conditions that could result in test failure. People with certain medical conditions or injuries, elderly people, and people who are seriously overweight often fail to pass standard field sobriety tests, sober or not. Moreover, test performance is often subjective, meaning whether you pass or fail is up to the officer conducting the test. For this reason, the field sobriety test is not mandatory in the state of Arizona, even though it is still widely used. Think twice before submitting to field sobriety tests. Performing poorly on these tests may provide the probable cause for your arrest, and even be used against you in court. However, any person stopped for suspicion of a DUI must submit to either a blood, breath, or urine test to determine impairment.

Breathalyzer tests calculate the amount of alcohol in a portion of exhaled air and multiply that amount by 2,100 to create a blood alcohol reading. This formula is used because the average sober body creates 1 part alcohol for every 2,100 parts of blood. The machines are calibrated to measure the alcohol vapor you exhale while taking into account the alcohol your body naturally produces. However, this formula does not take into account the fact that the ratio of alcohol to blood produced naturally in a human body fluctuates based on body temperature, hormone levels, the time of day, and respiration rate. This natural fluctuation can lead to a higher reading on a breathalyzer test. Another problem with the breathalyzer test is that it does not factor in alcohol-containing substances in the mouth, such as mouthwash, breath fresheners, medications, or regurgitated stomach fluid. The machine only examines alcohol content in the vapor exhaled, which could make the reading unnecessarily high. On top of everything else, there is always the possibility of the device malfunctioning. In all, the breathalyzer may not be an accurate representation of a person’s blood alcohol content.

One of the methods to measure blood alcohol content that is usually considered to be the most accurate, the blood test, is in fact not as reliable as once thought. Because each laboratory has its own procedures, the chemistry involved in analyzing the blood is not consistent. For example, if a blood sample is improperly preserved, it may coagulate or decompose, leading to an inaccurate high reading. Laboratories that conduct blood analysis run numerous samples on a daily basis, making it easy to have errors in some sample readings, especially if the lab does not follow standard record-keeping and organizational procedures.

The urine test is considered the least accurate of the tests for blood alcohol levels because the percentage of alcohol in the urine is not necessarily the same as the amount of alcohol in the bloodstream. This is because urine is stored in the bladder and remains there until it is emptied; therefore the contents in the bladder represent a shifting composite of an ever-changing blood alcohol content. For example, if a driver had four drinks a few hours ago and has not urinated since drinking them, their test results could be misleadingly high. The alcohol has had time to make its way through the system and be classified as waste by the body, but the driver simply has not gotten rid of it yet. Conversely, if a driver had been drinking non-alcoholic fluids and only had a few shots of alcohol minutes prior to taking a urine test, their blood alcohol content would appear very low because the alcohol has not yet made it to the urine. Finally, the same human errors in a laboratory setting that apply to blood tests apply to urine tests. Human error can and does happen.

If you are facing DUI charges, a skilled Arizona DUI lawyer such as Josh Blumenreich can advise you on your next steps. For a free initial consultation about DUI or other criminal charges, please contact us today.