If you were recently arrested and charged with driving under the influence (DUI) in Tennessee, you probably submitted to a chemical breath test. The State will likely try to use the results of that test as evidence against you in court if the results indicated that your blood alcohol concentration (BAC) was above the legal limit. Are those results accurate though? A Murfreesboro DUI lawyer at Bennett | Michael | Hornsby explains what factors might impact a DUI breath test.
The Tennessee Implied Consent Law
Once an initial traffic stop turns into a DUI investigation, a law enforcement officer will usually ask the motorist to perform a series of field sobriety tests. Sometimes, those tests involve the use of a portable breath test (PBT). The results of filed sobriety tests, including PBT results, cannot be used as evidence against you in court to prove that you were driving under the influence. Those results can only be used to establish probable cause for your arrest for DUI. Once you have been placed under arrest and transported to the jail or police station, however, you will be asked to submit to a chemical breath test. Like most states, Tennessee has an implied consent law that effectively says you give your consent to take a breath test if a law enforcement officer has probable cause to believe you were driving while intoxicated. While you can refuse to submit to a breath test, there are separate penalties that apply for a refusal.
How Does a Breath Test Work?
For several decades now, chemical breath test machines (commonly known as “breathalyzers”) have been routinely used when a motorist is arrested for suspicion of driving under the influence. Breathalyzers work by measuring your blood alcohol concentration (BAC), which is expressed as a percentage that equates to the weight of ethanol in grams for every 100 milliliters of blood. For example, a BAC of 0.08 means 0.08 grams of alcohol per 100 milliliters of blood. For most motorists, the legal limit is 0.08 in Tennessee. The legal limit may be lower if you have a CDL license or are under the legal drinking age (21).
When you drink an alcoholic beverage, the alcohol flows throughout your body through your bloodstream. As blood passes over your lungs, some of the alcohol evaporates into tiny air sacs in the lungs known as alveoli. When you exhale, the alcohol contained in the alveoli can be detected and measured. The amount of alcohol contained in the breath you exhale is directly related to the concentration of alcohol in your blood at a scientifically predictable ratio. While the mechanics of how a breath test machine works are well-known and widely accepted, they are far from infallible.
Factors That May Impact Breath test Results
Although the science behind the use of breath test machines is well established, there are several factors that can directly impact the results of a breath test, including:
- Improper calibration of the machine
- Lack of maintenance on the machine
- User error on the part of the machine operator
- Medical conditions, such as diabetes or gastroesophageal reflux disease (GRD)
- Burping or vomiting prior to taking the test
- Environmental exposure (such as being exposed to paint, which is high in acetone, at work)
- Residual mouth alcohol from mouthwash or other products that contain alcohol
- Certain over-the-counter and prescription medications
Along with factors that can directly impact the results of a breath test, additional factors can also be important to how results are interpreted. For example, the timing of the test compared to the time when you were driving can play a key role in your defense because of the rate at which your body metabolizes alcohol. Because there are so many ways in which a breath test result can be compromised, it is always best to have an experienced DUI defense attorney review the test results and evaluate the accuracy of those results.
Contact a Murfreesboro DUI Lawyer
If you have been charged with driving under the influence in Tennessee, it is in your best interest to consult with a Murfreesboro DUI lawyer at Bennett | Michael | Hornsby as soon as possible. Contact the team today by calling 615-898-1560 to schedule your free appointment.
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