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When a Tennessee police officer suspects a driver is under the influence of alcohol or drugs, the officer may ask the driver to perform field sobriety tests. These roadside exercises are used to observe balance, coordination, attention, and eye movements that an officer may associate with impairment.
Field sobriety tests can become important evidence in a DUI prosecution. However, the results do not tell the entire story. How the tests were administered, the conditions at the scene, and the driver’s physical condition may all affect the observations made by the officer.
Field sobriety tests are different from chemical tests such as breath or blood testing. Tennessee’s implied-consent law addresses chemical testing for alcohol or drugs and provides consequences for certain refusals of those tests.
A roadside field sobriety test is instead part of the officer’s DUI investigation. If an officer asks you to perform one or more field sobriety tests, the circumstances surrounding that request and what happens during the testing may become part of the evidence in your case.
If you are arrested for DUI after performing field sobriety tests, an attorney can examine what occurred during the traffic stop, how the tests were conducted, and what the officer reported observing.
The three standardized field sobriety tests are the Horizontal Gaze Nystagmus (HGN), Walk-and-Turn, and One-Leg Stand tests.
The tests are designed to evaluate different aspects of a person’s physical and mental performance. Officers are trained to look for specific clues during each exercise.
The Horizontal Gaze Nystagmus (HGN) test involves an officer moving an object, such as a pen or small light, from side to side while asking the person to follow it with their eyes.
The officer observes the person’s eye movements for specific clues during the examination. Because the test depends on the officer’s observations and how the examination is conducted, the circumstances surrounding the HGN test can be important in a DUI case.
The Walk-and-Turn is a divided-attention test. The officer gives the person instructions to take a series of steps, turn in a particular manner, and return.
The officer observes the person’s ability to follow instructions, maintain balance, and perform the exercise as directed.
A person’s performance can be affected by the surface, footwear, physical limitations, weather, or other conditions at the location where the test is performed.
The One-Leg Stand requires a person to raise one foot from the ground and maintain their balance while following the officer’s instructions.
The officer observes the person’s ability to maintain balance and complete the exercise. Physical conditions, injuries, age, balance problems, or the testing environment may affect performance.
Officers are trained to look for specific clues while a person performs the standardized field sobriety tests.
The presence of a particular clue does not necessarily mean that a person was impaired. The officer’s observations should be considered along with the instructions given, the conditions at the scene, the person’s physical condition, and the other evidence collected during the DUI investigation.
The accuracy of the officer’s report can also matter. What is written in a police report may not always provide the complete picture of what occurred during roadside testing.
Field sobriety tests are normally performed on the side of a road rather than under controlled conditions. A person’s performance may be affected by circumstances unrelated to alcohol or drug impairment.
Potential factors include:
These circumstances do not automatically invalidate a field sobriety test. They can, however, provide important context when evaluating what the test results actually show.
Field sobriety test evidence can be examined as part of a Tennessee DUI defense.
An attorney can review whether the officer properly administered each test, provided appropriate instructions, accurately identified the alleged clues, and considered the circumstances that could have affected the person’s performance.
The available video evidence may also be important. Dash-camera or body-camera footage can sometimes provide a more complete picture of the traffic stop and field sobriety testing than the written arrest report.
At Killen Law, we examine the details of the DUI investigation to identify weaknesses in the evidence and determine how they may affect the defense.
