Understanding field sobriety testing

If you're pulled over by the police on suspicion of drunk driving, then you'll likely be asked to perform a field sobriety test. This is not the breath test that measures your blood alcohol concentration. This test is actually a series of three different tests that allow an officer to determine if you are impaired.

Each section of the test helps by showing if you are balanced, if your pupils move correctly and if you can follow simple directions. The three tests include the walk-and-turn test, the horizontal gaze nystagmus test, and a final test, the one-leg stand.

Understanding the horizontal gaze nystagmus test

The HGN is a movement of the eyeball that occurs when you look to the side. When you're not intoxicated, and under normal circumstances, the eye only shows the HGN at high peripheral angles. When intoxicated, the nystagmus becomes exaggerated. Jerking of the eyes that is sustained and distinct may indicate intoxication.

Getting to know the one-leg stand test

The one-leg stand test is exactly what it sounds like. The officer asks you to stand on one leg and to balance for a period of time. The test usually lasts around 30 seconds or until the officer asks you to put your foot down. The trouble with this test is that many people cannot complete it, even when sober. Age, disease and injury can all impact the test.

Performing the walk-and-turn test

The walk-and-turn test is simple. You'll be asked to step forward for nine steps before turning on one foot and return to where you started. You also have to walk heel-to-toe and in a straight line. There are several indicators that a person could be impaired including not following the directions, using arms to balance, making an improper turn or stopping to regain their balance.

In many cases, people who are impaired will not be able to pass these tests. Although the tests are beneficial, there is a problem with them, too. Many individuals cannot pass them, even when they are sober. NGH tests might be failed by those with eye conditions or brain injuries, while both other tests require good balance and stability that not all people have naturally due to illness, disease or other issues.

When you're asked to perform field sobriety tests, it's possible to explain being unable to complete the tests due to personal health reasons. In court, these tests are often thrown out or not admitted because of the potential for sober individuals to fail them. In any case, they are still used today to determine if a person has been driving drunk.

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