DWI Field Testing Failure Rates

When the police suspect that a driver is under the influence of alcohol, they will generally conduct a series of tests in order to determine whether the driver is impaired and to gather evidence against them. The tests most often used are:

  • The Horizontal Gaze Nystagmus – Nystagmus is an involuntary twitching/jerking of the eyes that occurs when a person is under the influence of alcohol. When administering this test the officer asks the subject to track an object while he or she moves it from side to side. The officer observes the subject’s eyes, looking for signs of intoxication, such as lack of smooth pursuit and onset of nystagmus prior to 45 degrees.
  • The Walk and Turn – In the walk and turn, you are asked to take nine steps, heel-to-toe, on a line, and then turn around and return in the same manner. The officer administering the test will look for signs of intoxication, such as taking the wrong number of steps, using your arms to maintain balance, stepping off the line, or not walking heel to toe.
  • The One Leg Stand – The one leg stand requires you to stand on one leg while counting out loud, by thousands, until you are told to stop. The officer administering the test will look to see whether you sway, hop, use your arms for balance, or put your foot down, or show any other signs of intoxication.

These tests are usually performed at the scene of the traffic stop and involve the officer asking the suspect to perform certain tasks and observing them for signs of intoxication.

SFST and Gathering Evidence for DWI Arrest

Generally speaking, police officers do not ask people to perform the SFST without having already formed an opinion about whether they are intoxicated. As a result, field sobriety testing is often used more as a tool to gather evidence of intoxication than as a way to determine whether a driver is drunk. For this reason, in many cases, it may be advisable for drivers to refuse the field sobriety test and challenge the arrest (and DWI case) at a later date.

Field Sobriety Testing Reliability

In the 1990s, Dr. Spurgeon Cole of Clemson University conducted a study in order to determine how well police officers were able to determine whether a person was intoxicated based on the field sobriety testing alone. In the study, “Field Sobriety Tests: Are They Designed for Failure?” 14 police officers were shown video of 21 people taking common field sobriety tests. The officers were then asked, “Do you feel, as a law enforcement officer, that the following subjects, based on field sobriety tests performed on videotape, have had too much to drink to drive?”

46 percent of the responses from the officers indicated that a person had had too much to drink based on what they saw. In reality, all the individuals in the video were completely sober and had been verified at a 0.0 blood alcohol concentration (BAC) before the tests were conducted.

This is clear evidence that police officers are often biased in these investigations. That is specifically why you need an experienced attorney to challenge this one sided thinking.

Can You “Pass” the Field Sobriety Test?

Many people are under the mistaken impression that they can “pass” the field sobriety test. It is important to understand that the SFST is used more as an evidence gathering tool than a way for officers determine whether a person is drunk or not. In fact, if you have been asked to do the field sobriety test, there is a good chance that the police officer who pulled you over has already decided that you are intoxicated and is planning on arresting you regardless of how you perform on the test. For this reason, it is often advisable to refuse the test rather than give the police more evidence that can be used against you.

Watch our FAQ Videos.

Learn more about DUI/DWI Testing:

Field Sobriety Testing

Roadside Breathalyzers vs. Police Station Test

Arrested for DWI & Blew Over the Legal Limit

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If you have been arrested for DWI in the St. Louis area, you should call Muhlenkamp & Bernsen today. To schedule a free case evaluation with one of our lawyers, contact us at 314-499-7255.

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