Santa Cruz Good Times

Feb 06th
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Crime Time: Why Field Sobriety Tests Are Unreliable

If you get pulled over by an officer and he or she suspects that you’ve been drinking, you will be asked to perform a series of field sobriety tests (FSTs). The purpose of the FST is to judge whether or not your mental and physical abilities are too impaired by alcohol for you to drive safely. There are many different kinds of FSTs, but the three main ones are the horizontal gaze nystagmus (AKA the eye test), the one-leg stand, and the walk and turn. These three FSTs were deemed the most reliable by the National Highway Transportation Safety Administration (NHTSA). The problem is that they are not reliable. In fact, many people have been falsely accused and/or convicted of DUIs based on their poor performance during a field sobriety test.

FSTs are problematic because they are based on the subjective judgment of the police officer and factors other than alcohol consumption affect a subject’s performance. If you are accused of a DUI, it’s important that you understand the purpose of these tests and why the results are unreliable:

The Horizontal Gaze Nystagmus (AKA the eye test)

What it is: The definition of nystagmus is “congenital or acquired persistent, rapid, involuntary, and oscillatory movement of the eyeball, usually from side to side.” When officers administer the eye test to check for nystagmus, they are testing to see if the eyes track equally and smoothly, and they are also looking for equal pupil size.  To administer the eye test, the officer positions a stimulus 12 to 15 inches away from the subject’s nose and slightly above eye level. The officer then makes seven passes with the stimulus.

Why it’s unreliable: Officers often don’t do enough passes. They also fail to follow the correct timing protocol between passes, and they often misjudge the angle of the stimulus. Also, there are several causes of nystagmus, including drowsiness.

The Walk and Turn

What it is: The officer instructs the subject to take nine heel-to-toe steps while looking at his or her feet and counting each step out loud. The subject is then required to turn using a series of small steps and take nine heel-to-toe steps back.

Why it’s unreliable: Oftentimes, officers fail to designate a straight line for the subject to walk. Also, there are many factors that could impede a subject’s ability to walk in a straight line such as age, weight, and weather conditions.

The One-Leg Stand

What it is: The officer instructs the subject to raise one leg approximately six inches off the ground. The subject is required to keep his or her leg straight with toes pointed and count out loud for thirty seconds until told to stop.

Why it’s unreliable: One problem with this test is that the officer doesn’t always ensure that the surface is dry, hard, and level. There are also other factors that can affect one’s ability to balance such as age, weight, and back problems.

Many people who fail a field sobriety test believe the results are incontestable and that their only option is to plead guilty or no contest. That is not the case. If you or someone you know is arrested for a DUI based on a field sobriety test, make sure to consult a competent, experienced DUI lawyer.  If you have questions regarding a DUI arrest based on your failure of the field sobriety test, contact me at (831)-535-2363 or visit today.


TAGS: sobriety tests, santa cruz, dui, reliability of sobriety tests, drunk driving, lawyer, santa craz attorney. lars shalberg