What Are the Standardized Field Sobriety Tests?
If you've been pulled over by police and are suspected of drunk driving, chances are the officer asked you to perform some puzzling physical exercises on the side of the road. These are known as the Standardized Field Sobriety Tests (SFSTs), developed by the National Highway Traffic Safety Administration (NHTSA) to assist officers in determining whether a driver is impaired by alcohol or drugs. While the SFSTs are widely used, they are also commonly misunderstood by drivers. Having an accurate understanding of these roadside tests is important if you face OWI/DUI charges in the state of Michigan.
The Three Standardized Tests
The NHTSA has developed and standardized three tests that officers are trained to administer:
The Horizontal Gaze Nystagmus (HGN) Test
The Walk-and-Turn (WAT) Test
The One-Leg Stand (OLS) Test
Let's take a closer look at each one.
Horizontal Gaze Nystagmus Test
In the HGN test, the officer looks for an involuntary jerking of the eyes as they gaze towards the side. This jerking, known as nystagmus, is one possible indicator of impairment by alcohol or certain drugs. The test involves the officer moving a stimulus (like a pen or flashlight) slowly across the driver's field of vision to look for three specific clues in each eye: 1) The inability of the eye to smoothly pursue and track the moving stimulus 2) Distinct jerking/bouncing of the eye when it moves to the side 3) Angle of onset of jerking before 45 degrees. If four or more clues are observed between both eyes, research suggest that this may indicate a blood alcohol concentration (BAC) over the legal limit of 0.08.
Walk-and-Turn Test
In the WAT test, the driver is instructed to take nine heel-to-toe steps along a straight line, turn in a prescribed manner, and take nine steps back. The officer looks for eight possible clues of impairment: 1) Cannot keep balance while listening to instructions 2) Starts before instructions are finished 3) Stops while walking to regain balance 4) Does not touch heel-to-toe 5) Steps off the line 6) Uses arms to balance 7) Loses balance on turn/turns incorrectly 8 ) Takes the wrong number of steps If the driver exhibits two or more of these clues, it may indicate intoxication.
One-Leg Stand Test
For the OLS test, the driver must stand with one foot about six inches off the ground and count aloud by thousands (1000-one, 1001-one thousand one, etc.) until told to stop. The officer times this for 30 seconds and looks for four possible clues: 1) Swaying while balancing 2) Using arms for balance 3) Hopping to maintain balance 4) Putting the raised foot down If the driver exhibits two or more of these clues, it may indicate impairment.
Limitations of the SFSTs
While the standardized tests are widely used, it's important to understand some of their key limitations: The tests were developed as screening tools, not as actual evidence of a specific BAC. Just because someone exhibits certain clues does not definitively prove they are over the 0.08 legal limit.
The tests require giving long, complex instructions which can be misunderstood or forgotten, especially under stressful conditions. This can lead to failing the tests for reasons unrelated to impairment.
Many non-alcohol related conditions can produce similar clues, including age, weight, injuries, fatigue, medical conditions, footwear, weather/lighting, and nervousness.
Officers must follow strict administration and scoring standards. Any deviations can undermine the tests' reliability.
The tests were developed for estimating alcohol impairment only. Their ability to detect drug impairment is more limited. So while the SFSTs can be useful tools for officers, they have significant limitations and should not be considered conclusive proof of intoxication or impairment.
Attorney Aaron Martinez is one of Michigan’s only members of the National College for DUI Defense, an organization of drunk driving defense practitioners across the United States. This organization commits itself to high standards of scientific lawyering to hold the government to its high burden of proof. If you have been arrested for drunk driving in the state of Michigan, Attorney Aaron Martinez has the skills to help you defend your name - call for a free consultation today at (877) AARON-4U.