Daniel J. Wright
Drug and Alcohol Tests for DUI: Just How Accurate Are They?
If you are stopped by a police officer and suspected of driving under the influence of alcohol or drugs, you will be asked to take tests. The first would be a standard field sobriety test, after which you may be required to take one that is more extensive to detect the presence of alcohol or drugs in your system. These tests can check your breath, blood, or urine. However, in many cases, there may be a question of the accuracy of these tests. It is worth exploring how they work and how accurate they are in any given scenario.
It should come as no surprise that tests that involve a blood sample to detect the presence of alcohol or drugs are the most accurate. However, an experienced drunk driving lawyer might find problems with this testing, such as the competency of the individual conducting the test and the efficacy of the testing equipment. Issues that could come up during a DUI case include blood samples that are improperly preserved and sit around too long prior to being analyzed. Such a blood sample could coagulate or decompose, leading to a falsely high reading.
In addition, because laboratories analyze numerous blood samples on a daily basis, with some components tested in separate vials, it’s common for errors to occur. Usually, errors happen when the lab doesn’t have good organization or record keeping.
In both of these scenarios, the possibility of an error in blood testing to determine the presence of alcohol or drugs is slim. Generally, the blood sample analysis will be accurate.
Breath tests, also known as breathalyzers, are administered on the scene by a police officer. Because of the rushed nature of this particular test and the fact that it is conducted in an open environment, there can easily be errors.
A breath test to detect alcohol from air that is exhaled works by taking the alcohol content and multiplying by the number 2,100. This number is known as a partition ratio and is used because lung air that is exhaled by an average person usually contains 1/2100th the amount of alcohol than the same amount of blood.
In other words, the breath test is less accurate because it involves a rough estimation. Additionally, the value for even a single person varies depending on body temperature and rate of respiration. As a result, it’s not uncommon for the calculated blood alcohol level to be incorrect.
On top of these errors, there can also be false readings if a person has taken substances that contain alcohol, such as prescriptions or over-the-counter medications, mouthwash, or has even vomited. If those substances are present in the mouth within 20 minutes of taking a breathalyzer, the reading can be inaccurate.
Another thing that can lead to an erroneous reading in a breath test is a malfunction in the testing device. Testing devices must be properly calibrated and serviced.
The urine test is the least accurate when trying to detect alcohol or drugs in a person’s system. As a result, it is only used when blood and breath tests are unavailable. A major reason why they tend to be inaccurate is that a urine test must be correlated to a blood alcohol level. In addition, there have been studies done that show that some people have alcohol levels only 40 percent in their urine compared to in their blood. Others may have twice the level of alcohol content in the urine versus the blood.
Urine samples also continuously change the blood alcohol content, which can give an inaccurate test result.
If you have been arrested on suspicion of a DUI, it’s important to hire a DUI attorney such as the DUI attorney DC locals turn to represent you. If there’s any chance that your charges could be thrown out due to an inaccurate test, you’ll want to have an experienced and thorough lawyer representing your best interests in court.
A special thanks to our Author at The Law Firm of Frederick J. Brynn P.C. for their insight into Criminal Law.