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Field Sobriety Tests: What You Need to Know

On Behalf of | Jan 23, 2015 | OVI, OVI Defense |


Why do police officers make suspected drunk drivers stare at a pen, stand on one leg, and walk a straight line? These “tests” are called “Standardized Field Sobriety Tests” (SFST) and were developed in the late 1970s and early 1980s as a way for law enforcement to establish a standardized method to help them determine whether an individual is too impaired to drive. However, these tests are actually meant to predict the probability that an individual’s Blood Alcohol Content (BAC) is higher than .08, the legal limit in most states.

What my client’s often refer to as the “pen test” is actually called the Horizontal Gaze Nystagmus test or HGN. HGN is an involuntary jerking of the eye as the eye moves horizontally while following a moving stimulus. The officer checks for three types of nystagmus in both eyes, for a total of six possible “clues” that someone would test over a .08. If the officer observes a total of at least four of the six possible clues (three clues in each eye), there is a 77 percent probability that the individual would test at a .08 BAC or higher.

The other two field tests, the Walk and Turn and the One Leg Stand, are obviously balance and coordination tests. However, they are also meant to test an individual’s ability to listen to and follow directions. The Walk and Turn has a 68 percent probability of predicting that an individual has a BAC of .08 or higher and the One Leg Stand is accurate about 65 percent of the time.

Perhaps the most important thing to know about field sobriety tests? You can respectfully and politely refuse to take them. Although it is likely that you will be placed under arrest if you refuse these tests, the State will have less evidence to prove your impairment to a judge or a jury. The less evidence the State has, the better your chances of avoiding an OVI/DUI conviction.

Attorney Jessica D’Varga dedicates her practice to defending OVI, criminal, and traffic charges in Columbus, OH as part of the award-winning team at The Law Offices of Saia, Marrocco & Jensen Inc. Contact the firm to schedule a free initial consultation.

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