Disputing the Field Sobriety Tests – “Failure” doesn’t necessarily mean intoxicated. (Part A)

Field Sobriety Tests (FSTs) are designed to test both physical coordination and cognitive abilities. FSTs are used by the officer both for probable cause to arrest and evidence of guilt at trial. The problem with FSTs is three-fold: (1) sometimes medical and physical conditions unrelated to alcohol consumption can result in a poor performance on the FSTs and be mistaken for intoxication; (2) most FSTs have no scientific correlation to whether someone is impaired by alcohol (for example, one study found that 78% of test subjects who were sober were unable to successfully complete one of the most commonly offered FSTs), and (3) in order to draw any limited meaningful conclusions from the results of FSTs, an officer must be properly trained in administering the tests and must administer the tests correctly. If there is a breakdown in the procedure, the results can be called into question.

Standardized DUI/DWI Field Sobriety Tests Used in Virginia

There are three major studies that have evaluated FSTs. These studies were conducted in conjunction with or sponsored by the National Highway Traffic Safety Administration (NHTSA). There are only three FSTs that became standardized field sobriety tests as a result of the NHTSA validation studies. These are the Horizontal Gaze Nystagmus (HGN), the One Leg Stand, and the Walk and Turn.

It is important to note that the results of the validation studies were premised on three things: (1) the tests being administered in the prescribed standardized manner; (2) the use of standardized clues to assess the suspect's performance, and (3) the use of standardized criteria to interpret the performance. If any one of these elements is changed, the validity of the studies is compromised.

FST #1 - Horizontal Gaze Nystagmus

You are instructed to stand with your feet together and your arms at your sides. You must follow a stimulus with your eyes only; you are not to move your head when tracking the stimulus. The stimulus is usually a pen or light held 12 to 15 inches in front of the suspect, slightly above your eyes. The police officer must first determine if you are a proper candidate for the test. The police officer will check for equal pupil size and even tracking of the stimulus with a series of passes from your left to right. If you cannot track the stimulus, it may be an indication of a medical disorder or blindness. If the pupils are not of equal size, this may indicate a head injury or that the suspect has ingested a heavy narcotic. If either event occurs, the test should not
be conducted.

  • Lack of Smooth Pursuit - The test begins with the police officer checking for lack of smooth pursuit. The stimulus will be moved in a quick, steady pace from your left to right. This action occurs twice. The police officer is looking for the eye to make "jerking" movements as they follow the stimulus.
  • Distinct Nystagmus at Maximum Deviation - During this portion of the test, the officer will move the stimulus to a point where your eye cannot move in that direction any further. The white of the eye will not be showing. The stimulus is held at this position for four seconds. The officer will look for "jerking." This is done twice for each eye.
  • Onset of Nystagmus Prior to 45 Degrees - During this segment, the officer will move the stimulus in the same manner it is moved during lack of smooth pursuit. However, the speed of the moving stimulus is significantly reduced. It should take four seconds to move the stimulus from the nose to the left shoulder or right shoulder, depending on which eye the officer is evaluating. If the police officer detects nystagmus while moving the stimulus out to the shoulder, the officer must determine if the nystagmus persists. If the nystagmus persists, the findings are recorded in the police report. If the nystagmus stops, the officer will continue to move the stimulus toward the shoulder.

There are a total of six clues. Each eye is evaluated with the three tests. If the suspect triggers at least four clues, the police officer interprets this as a "failed" test.

To get meaningful results from the test, it is necessary that the test be performed in the correct manner. The officer must move the pen at a certain speed and make observations at certain angles. More importantly, there are numerous medical conditions and other external factors that can cause the type of jerking normally associated with impairment. These issues must be explored on cross-examination.

While this test is considered by some to be accurate, it is the test most often excluded from evidence during hearings and trials. In order to get the results of this test before the judge or jury in a DWI/DUI case, the prosecutor must establish a proper evidentiary foundation for the admissibility of the test. Given the conditions set by the state and the science underlying the HGN test, it is very difficult for a prosecutor to do this without an expert. Testifying officers simply do not have the scientific or medical training to provide this foundation.

Continue to Part B of this article.

If you have a pending DUI/DWI and would like to discuss your case with a former prosecutor that has handled cases on both sides of the system, call 703-556-0004 or use the Contact Us page to review your case with a Fairfax Virginia DUI DWI Criminal Defense lawyer.   

Kyle Manikas
Connect with me