Can You Challenge DUI Evidence? Understanding Breathalyzer and Field Sobriety Tests
March 27, 2025
When you face a DUI charge, the evidence against you, such as breathalyzer results and field sobriety test performance, can make or break your case.
In Tennessee, like in many states, DUI laws are strictly enforced, and the evidence collected during your arrest plays a significant role in determining the outcome of your case. But can you challenge that evidence?
The short answer is yes.
There are various ways to challenge DUI evidence in court, and understanding how to do so can make a significant difference in your defense. The best way to help your case is to partner with me at The Law Office of Sheridan Randolph for skilled defense representation.
Here, I’ll explore how DUI evidence, including breathalyzer tests and field sobriety tests, can be contested and what avenues are available for a solid DUI defense. Whether you’re seeking information for yourself or someone else, it's important to understand the process and how it might play out in Tennessee courts. Contact my Cleveland, Tennessee, firm today to get personalized legal support.
Breathalyzer Tests in DUI Arrests
Breathalyzer tests have become one of the most common methods of testing a driver's blood alcohol concentration (BAC). When a person is arrested on suspicion of DUI, the officer may request that the driver blow into a breathalyzer device.
If the test results show a BAC over 0.08%—the legal limit for most drivers in Tennessee—the individual is presumed to be driving under the influence. However, there are several ways to challenge the results of a breathalyzer test. It’s essential to recognize that the accuracy of the breathalyzer test isn’t always guaranteed.
These devices can be affected by various factors, leading to inaccurate results. For instance, improper calibration, failure to follow procedure, or even certain medical conditions can result in a breathalyzer providing faulty results.
Common Issues with Breathalyzer Tests
Several factors can influence the reliability of a breathalyzer test, which can lead to a successful DUI defense if they’re identified. Here are some key issues:
Improper calibration: Breathalyzers need to be calibrated regularly to make sure their accuracy. If the device hasn’t been calibrated properly, it could produce false readings, leading to an incorrect BAC result.
Officer error: Law enforcement officers must follow specific procedures when administering the test. Failure to adhere to these procedures, such as not waiting the proper amount of time between the arrest and administering the test, can undermine the results.
Medical conditions: Certain medical conditions, such as acid reflux or diabetes, can affect breathalyzer results. For instance, someone with acid reflux might have alcohol in their mouth due to stomach acid, which can skew the reading.
Mouth alcohol: If a person burps or has alcohol in their mouth (from a recent drink or from mouthwash), this can lead to inaccurate readings. Proper testing procedures are designed to avoid this, but if they’re not followed, the results may not reflect the person’s actual BAC.
How to Challenge Breathalyzer Results
To challenge breathalyzer evidence, your DUI defense lawyer can argue that any of the above factors may have affected the accuracy of the test results. They can also request the maintenance and calibration records of the breathalyzer to determine if the device had been properly maintained.
Furthermore, they may question whether the officer followed the correct procedures when conducting the test. If your lawyer can demonstrate that the breathalyzer was unreliable or improperly administered, the prosecution may have difficulty using those results as evidence. This strategy can be helpful when challenging field sobriety tests as well.
What Are Field Sobriety Tests and How Can They Be Challenged?
Field sobriety tests (FSTs) are another common method used by law enforcement officers to assess whether a driver is under the influence. These tests are designed to evaluate a person's coordination, balance, and ability to follow instructions. In Tennessee, the most commonly administered FSTs include:
Horizontal Gaze Nystagmus (HGN): This test involves the officer asking the driver to follow a moving object with their eyes. A person’s eyes may involuntarily jerk when they are intoxicated, which can be a sign of impairment.
Walk-and-turn test: In this test, the driver is asked to walk in a straight line, turn, and then walk back. Impairment may be indicated by stumbling or failure to follow instructions.
One-leg stand test: The driver is asked to stand on one leg for an extended period. Inability to balance could suggest impairment.
Like breathalyzer tests, field sobriety tests can also be challenged in court since they do have flaws.
Issues with Field Sobriety Tests
Several factors can affect a person’s performance on FSTs, even if they’re not impaired. Some common issues that may impact FST results include:
Weather and terrain conditions: Slippery or uneven ground can make it difficult for anyone to perform these tests properly, even if they’re sober. If the tests were conducted on a rainy or uneven surface, it may provide a valid reason for a failed test.
Medical or physical conditions: Certain medical conditions, such as leg injuries, arthritis, or balance issues, can make it harder for a person to complete the tests. Officers are often not aware of the driver’s medical history, which can lead to unfair assessments.
Nervousness or stress: Being pulled over for a suspected DUI can be stressful, which may affect a person’s ability to concentrate or perform physical tasks. Some individuals may fail FSTs simply because they are anxious about the situation.
Improper administration: Field sobriety tests must be administered in a consistent manner according to protocol. If the officer did not follow proper procedure—such as not explaining the test correctly or not giving the driver enough time to perform the task—it can undermine the results.
How to Challenge Field Sobriety Tests
To challenge the results of field sobriety tests, your DUI defense lawyer can focus on the circumstances under which the tests were conducted. For example, they may argue that the weather or road conditions were unsuitable for the tests.
Additionally, they could highlight any medical conditions or physical limitations that could have interfered with the person’s performance. In some cases, your lawyer may even argue that the tests were not properly administered, which can render the results inadmissible. Having this experienced professional by your side can make or break your case.
The Importance of a DUI Defense Lawyer
Challenging the evidence in a DUI case, including breathalyzer and field sobriety test results, requires a deep understanding of both the science behind these tests and the legal procedures involved. In Tennessee, DUI defense lawyers play a crucial role in overseeing that all aspects of your case are carefully examined.
They can help uncover weaknesses in the prosecution’s evidence and fight for the best possible outcome on your behalf. If you’ve been arrested for DUI in Tennessee, don’t assume that the evidence against you is automatically ironclad.
There are often ways to challenge the results of breathalyzer tests or field sobriety tests, and a qualified DUI defense attorney can explore these options for you. A solid DUI defense can make all the difference in the outcome of your case.
Connect With My Firm Today
If you’ve been charged with DUI in Tennessee, consulting with a DUI defense lawyer is essential. I’ll review all aspects of your case, identify potential weaknesses in the evidence, and help you traverse the legal process effectively. With the right legal representation, you may be able to challenge the evidence against you and secure a favorable outcome. Reach out to The Law Office of Sheridan Randolph in Cleveland, Tennessee today for more information.