When you are stopped on suspicion of a DUI/DWI in Texas, you may be asked to submit to Standardized Field Sobriety Testing (SFST). As the SFST Training Program explains, one of the goals of the test is to determine whether a person has been driving while intoxicated and to make DWI investigations more consistent. However, field sobriety tests often are inaccurate. To be clear, field sobriety tests are very different from breathalyzer tests or blood tests. Rather than using a device to determine a person’s blood alcohol concentration (BAC), a field sobriety test requires a driver to respond to certain questions and to perform specific tasks, at which point the law enforcement officer makes a decision about whether the driver has “passed” the test or not. If the driver does not pass the test, then the driver can be charged with a DWI, for which you will want to consult with a DWI attorney in Austin.

As a report from NBC News emphasizes, it is difficult to pass a field sobriety test whether you are drunk or sober. Anxiety and bad coordination, for example, often lead to false positives—situations in which a driver fails a field sobriety test but simply is not driving while intoxicated according to Texas law. To better understand the problems with field sobriety tests, it is important to understand how they work. Then, we will tell you more about how these tests frequently lead to false positives. If you failed a field sobriety test, an Austin DWI lawyer can help.

How Do Field Sobriety Tests Work?

In general, there are three types of tests that make up the field sobriety test (FST), including:

What is involved in each of these tests? The horizontal gaze nystagmus is designed to see if the driver’s eye involuntarily jerks, which can sometimes be a sign of alcohol impairment. Both the walk and turn test, as well as the one-leg stand test, seek to determine how well a person follows instructions and how good the person’s balance is—both things that can be disrupted by alcohol impairment.

However, as you might imagine, determinations as to who passes these tests can be extremely subjective. Moreover, there are many reasons that a person might fail these tests for reasons other than alcohol impairment. According to the NBC News report, the horizontal gaze nystagmus test only has an accuracy rate of 77 percent, while the accuracy rates of the other two tests are even lower. The walk and turn test has a 68 percent accuracy rate, while the one-leg stand test only has a 65 percent accuracy rate.

Reasons a Field Sobriety Test Can Be Inaccurate

We emphasized that field sobriety tests often lead to false positives and that their accuracy rates do not instill confidence in the ability of these tests to determine a person’s alcohol impairment level. Common reasons for false positives include but are not limited to:

These reasons for false positives, in addition to others, can provide a defense to a failed field sobriety test.