Does the Standardized Field Sobriety Test Accurately Determine whether a Driver is Drunk?


When law enforcement officers suspect that a driver is under the influence of drugs or alcohol, they usually engage in investigative techniques designed to obtain evidence of intoxication. In order to convict someone of driving under the influence of alcohol or drugs (DUI) the state must be able to establish the fact that a person was intoxicated beyond a reasonable doubt, which is the highest burden of proof in the American legal system.

There are a number of ways in which a law enforcement officer can obtain evidence of intoxication, including the chemical testing of a person’s blood, breath, or urine or simple observations regarding a driver’s appearance and behavior. The Standardized Field Sobriety Test, or SFST, was developed by the National Highway Traffic Safety Administration (NHTSA) in order to create a standardized test that can help law enforcement identify drunk drivers. The SFST is actually a battery of three tests, which include:

  • The Horizontal Gaze Nystagmus (HGN) test – When a person gazes to the left or right, an involuntary jerking of the eyes often occurs at high peripheral angles, known as nystagmus. Nystagmus occurs at lesser angles and is exaggerated when a person is under the influence of alcohol. To perform the HGN test, a law enforcement officer asks an individual to track the motion of an object from side to side while observing his or her eyes.
  • The One-Leg Stand Test – The One-Leg Stand test involves a person standing on one leg for 30 second while an officer observes the subject looking for signs of intoxication.
  • The Walk-and-Turn Test – In this test, the officer administering the test asks that the subject take nine steps, heel-to-toe, and then turn around an return in the same manner. Again, the officer administering the test observes the test subject for signs of intoxication.

Of course, the investigative and evidentiary value of the SFST depends on its accuracy. According to a study conducted in 1998, officers were accurate in making determinations of intoxication 94 percent of cases when all factors were combined. However, older research indicated that officer’s arrest decisions were correct 81 percent of the time when all three tests were administered. While these numbers may seem to indicate that the test is relatively accurate, it is important to remember that it not foolproof. In other words, there are cases in which an officer determines that someone is intoxicated to the extent that he or she is over the legal blood alcohol content (BAC) limit based on their performance on the SFST when they are not. In addition, there may be other factors that can affect a person’s performance on the SFST other than intoxication, including the following:

  • Medical conditions
  • Physical limitations
  • Allergies
  • Fatigue or drowsiness
  • Illness

In some cases, the officer administering the test was not properly trained in how to administer the test or how to accurately evaluate a person’s performance on the test.  When problems with the administration of the SFST such as those listed above exist, it may result in the invalidation or even the exclusion of the test results in any proceeding against a suspected drunk driver.

Contact a Denver DUI defense lawyer today for a free

Individuals who are accused of DUI in Denver and the surrounding areas are often facing serious legal penalties. As a result, it is extremely important for anyone arrested for DUI to contact an experience an attorney as soon as possible. To schedule a free consultation with one of our DUI defense attorneys call the Tiftickjian Law Firm today at (303) DUI-5280.

Photo Credit: Jason Rojas

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