You are driving, and you see the flash of police lights behind you. You pull over to the side of the road. The stop can end in three ways: with a warning, with a ticket, or with an arrest.
Often, those who are arrested after a traffic stop are done so because the officer alleges that he has probable cause to believe that they were driving under the influence (DUI/DWI). Officers initially suspect that someone is driving under the influence due to an odor of alcohol, red face, bloodshot eyes, watery eyes, an admission that the driver has been drinking, or some other indication that the driver has consumed alcohol.

The officers usually “verify” or “test” their suspicion by requesting that the driver participates in standardized field sobriety testing. Often, the results of these field sobriety tests grant the officers the necessary “probable cause” for the DUI/DWI arrest.

DUI Field Sobriety Tests

There are usually three field sobriety tests administered by the officer. The first is called the Horizontal Gaze Nystagmus (HGN) test. This test is conducted by the officer holding up a pen in front of the driver’s face and asking the driver to follow it with just his or her eyes. The HGN test examines nystagmus, which is an involuntary jerking of the eye that can be affected by the consumption of alcohol. The second test is called the walk and turn test, which requires the driver to walk heel-to-toe along a straight line for nine steps, pivot, and then walk back. The third test is called the one leg stand test, which requires the driver to stand on one leg with the other leg extended in the air for thirty seconds. Both the walk and turn and the one leg stand test examine the driver’s coordination, balance, and ability to apply multiple directions at once.

If the driver does not consent to breath or urine testing, the field sobriety tests are often the majority of the government’s evidence in a Driving Under the Influence case. But how reliable are the tests in determining whether a person is intoxicated?

Poor Performance Due To Comprehension Problems

The DUI field sobriety tests can actually be affected by many factors other than intoxication. For example, an individual can perform poorly on a field sobriety test simply because they had difficulty comprehending and immediately applying the instructions.

The officers rattle off the instructions in the beginning of the test, often speaking quickly because they are repeating the same words that they have said countless times throughout their career. The individual, who is usually hearing these instructions for the first time, is expected to listen carefully to the officer, understand a series of very specific instructions, and immediately apply multiple instructions without any opportunity to practice to make sure that they understand all of the requirements.

The individual is expected to do all of this while simultaneously undergoing the stress of being pulled over and confronted by an armed, uniformed police officer who may arrest them at any minute.

Anyone who has been in terrifying situations knows that can be difficult to think with a clear head. In a stressed state, it is easy to let your mind skip over a few words uttered by the officer or forget to apply some of the instructions while performing the test. In a field sobriety test, simply not paying attention to a few words like “walk nine steps” or “count out loud” can be the difference between passing and failing the test – even though the lapse was simply due to the stress and not due to intoxication.

This difficulty comprehending and instantaneously applying the instructions can be difficult for anyone – but can be particularly difficult if someone suffers from a learning disability. The officers, however, do not ask the individual’s level of education or if they suffer from any disabilities prior to administering the test. Therefore, a poor performance of the DUI/DWI field sobriety tests may be simply due to a difficulty comprehending the information, but will be viewed by the officers and the court as evidence of intoxication instead.

Poor Performance Due to Innate Lack of Coordination

Apart from the stress and difficulty inherent in the field sobriety tests, an individual may perform poorly on the tests simply because some people are naturally less coordinated than others. Balance and coordination are not always inherent, as those of us who are chronically clumsy can attest.

In particular, the one leg stand requires the individual to balance on one foot for thirty seconds. While this may be simple for a police officer who has to pass physical examinations, not everyone has the physical strength to accomplish this feat. As anyone who has had to hold their leg up in a Tree pose during a beginners Yoga class can understand, balancing on one leg can be extremely difficult – and not being able to do so can have absolutely nothing to do with the consumption of alcohol.

The Field Sobriety Tests Are Not Reliable

There are countless factors that can lead to a poor performance on a field sobriety test that is not indicative of consumption of alcohol or drugs. Therefore, despite its widespread use, the field sobriety tests are not reliable indicators of intoxication.