The Weaknesses of DWI Field Sobriety Tests

Published on April 12, 2021 Science & DWI

Updated: Nov 22, 2021 @ 2:21 pm

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When someone is pulled over on suspicion of drinking and driving, one of the officer’s first responses will probably be to conduct a field sobriety test. These tests, which are meant to test a person’s coordination and focus, are unfortunately, not always accurate. It is, however, often possible to have these tests thrown out, especially if there is evidence that they were administered improperly, so if you were recently arrested for or charged with a DWI, you should certainly speak with an experienced drunk driving lawyer in Houston about building a defense.

Types of DWI Field Sobriety Tests

In Texas, standard field sobriety tests usually consist of three separate tests, including:

The One-Leg Stand Test, which requires the driver to balance on one leg for around 30 seconds;
The Walk-and-Turn Test, which requires the subject to walk heel-to-toe in a straight line for a certain distance; and
The Horizontal Gaze Nystagmus Test, in which a driver is asked to follow an object with his or her eyes, while it is being moved horizontally by the officer.

During the administration of each of these tests, officers are directed to examine the subject’s balance, ability to follow instructions, coordination, and to remain vigilant for any other signs of intoxication. Failing even one of these tests can result in a DWI charge. This is unfortunate and sometimes unfair, as there are a number of questions about the accuracy of these kinds of tests.

The Faults of Field Sobriety Tests for Alcohol

One of the biggest concerns about field sobriety tests is their reliability. The horizontal gaze nystagmus test, for instance, which is considered to be the most accurate of the three tests, only has a 77 percent accuracy rate. Experts have also expressed concern about how these tests are administered, as a lack of training or even a minor misstep in procedure could produce inaccurate results. Confusing or contradictory instructions, for instance, could make it seem as though a driver is inebriated. In other cases, a driver could have a mental or physical handicap that affects his or her performance, a fact that may be unknown to the officer if he or she failed to ask the proper questions. These tests, which are partially based on an officer’s subjective opinions, are also more at risk of being affected by officer bias.

Why do Drivers Routinely Fail Field Sobriety Tests?

Aside from the cases where a person is actually inebriated, a failed field sobriety test is often the result of:

Anxiety, which often manifests physically as muscle tension, shakiness, and uncontrollable movements;
Fatigue, which can also cause muscle tension and confusion;
The side effects of certain prescription medications; and
Misunderstanding the instructions, whether due to an actual inability to hear the officer, or to an officer’s unclear explanation.

Field sobriety tests are not foolproof methods of determining whether a driver is intoxicated. If you’re facing DWI charges in Houston, you may want to consider challenging the results of your test in court.