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In Mississippi and throughout the nation, law enforcement officers use field sobriety tests (FSTs) as a preliminary evidence-gathering tool when they suspect drunk driving. These are tests of physical coordination and the ability to follow directions. The standard tests include the one-leg stand, the walk-and-turn test and the horizontal gaze nystagmus (where the test taker follows a moving object with their eyes).

These three standard FSTs are endorsed as reliable by the National Highway Traffic Safety Administration. But are they actually an accurate way to determine if someone is likely impaired by alcohol? Considering that a person could easily fail these tests even when completely sober suggests that they are not.

Below are some common reasons why sober drivers fail field sobriety tests.

Physical impairments and balance issues

Just as some people maintain great balance and coordination when drunk, others struggle from balance and coordination issues when sober. If you have a health condition with symptoms that include muscle weakness or vertigo, for instance, it might be very difficult to pass an FST, even if you don’t have a drop of alcohol in your system.

Test anxiety is real

Some people don’t do well under pressure, and getting pulled over definitely qualifies as being under pressure. If you panic at the thought of taking a high-stakes test, you may be unable to pay attention to directions or more likely to make mistakes.

Also, did you know that consuming alcohol can lead to feelings of anxiety after sobering up? Alcohol changes the levels of neurotransmitters in the brain, and some people feel anxious for several hours or even a full day after the alcohol has left their system. Imagine staying at a friend’s house for hours in order to sober up, only to be pulled over on your way home. If you are feeling some latent anxiety, it could impact your test performance.

Poor testing conditions

Much of the time, DUI traffic stops occur on the side of a busy road or highway at night. It is loud, cars are driving by and you are being blinded by passing headlights. Most of us would perform poorly under conditions like this – and people do, even when sober.

Considerations in a DUI case

Thankfully, field sobriety tests are almost never the sole source of evidence used to arrest someone on suspicion of drunk driving. Instead, they are usually a pretext for police to request additional testing from the driver (often a breathalyzer). But if you are eventually arrested and charged with drunk driving, FST results may be used against you in court. With the help of an experienced criminal defense attorney, however, this and other evidence from the stop can be challenged or even suppressed.