The limitations of field sobriety tests

Many of us have seen, either in person or through a media representation, someone performing a field sobriety test (FST). There are a wide range of standardized and non-standardized tests used by law enforcement agencies across the country.

Some FSTs try to evaluate a potential defendant’s mental state, while others assess physical reactions.

Common mental/thought process tests include reciting the alphabet without singing or saying it backwards. It is important to note that, while they may be persuasive to an officer, no mental/rational FSTs are widely accepted for standardized use.

The three most common physical tests used are the ones officially sanctioned by the National Highway Traffic Safety Administration. These are:

  • Horizontal gaze nystagmus (following the officer’s finger or a light with the eyes without turning the head); however, this test is not admissible in Tennessee and an experienced DUI attorney will know how to challenge this test.
  • One-leg stand (standing on a chosen foot at the officer’s direction with your other foot held above the ground and counting for a set time)
  • Walk-and-turn (walk by putting one foot in front of the other, heel-to-toe, in a straight line, then turning and going back to the starting point)

Interpreting results of FSTs

The NHTSA provides guidance in the form of a study-based validation report that can help officers administering FSTs interpret the results. Of course, the interpretation is still subjective according to the officer’s perspective, and does not take into consideration variables that could potentially impact the results, including:

  • Physical conditions (age, weight, inner-ear disturbances, joint problems and other mobility issues or injuries can make a one-leg stand or walk-and-turn impossible for some people)
  • Hearing loss (if the alleged suspect cannot clearly hear the officer’s instructions, he or she might stand on the wrong leg)
  • Medications (some medicines can cause eye twitching or gaze interruptions that could be misinterpreted as signs of intoxication)
  • Prior brain injuries can impact the reliability of the horizontal gaze nystagmus, even without causing sufficient vision disturbances to affect the person’s driving privileges
  • Wording of the instructions by the officer and whether or not the officer gave the complete or correct instructions can affect how a person performs the tests

As you can see, there are many possible reasons why field sobriety test results could be challenged. Without admissible test results, the charges against you might be reduced or dismissed. If you’re facing DUI charges, contact a skilled criminal defense attorney as soon as possible who has the training necessary to effectively challenge field sobriety tests.

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