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What do field sobriety tests look for?

On Behalf of | Aug 3, 2018 | DUI/OUI |

Just about everyone knows that police officers perform field sobriety tests in order to determine whether an individual is impaired and unable to drive safely. The National Highway Traffic Safety Administration helped create and test a battery of three tests known as the Standard Field Sobriety Test.

The SFST includes the walk-and-turn test, the horizontal gaze nystagmus test and the one-leg stand test. Each part of the SFST evaluates certain aspects of an individual. Supposedly, the SFST indicates impairment with a 90 percent success rate.

What does the walk-and-turn test look for?

In this test, you would walk in a straight line, heel to toe for nine steps. You then turn around and repeat the process in the opposite direction. The officer administering the test looks for the following:

  • Did you begin the test before the officer completed the instructions?
  • Did you maintain your balance while listening to the instructions?
  • Did you fail to touch your heel to your toe?
  • Did you have to stop to regain your balance?
  • Did you use your arms to maintain your balance?
  • Did you fail to take nine steps?
  • Did you lose your balance while turning?

The NHTSA says that if you answer yes to two or more of the above questions, the likelihood that your blood alcohol concentration is .10 or higher is 68 percent. That leaves a significant margin of error.

What does the horizontal gaze nystagmus test look for?

Anytime you move only your eyes to the side, they involuntarily jerk. This happens to everyone. However, the NHTSA says that these jerking movements become exaggerated in someone who is drunk. When administering this test, the officer looks for the following:

  • Was the jerking distinct at maximum deviation of your eye?
  • Was your eye able to smoothly follow an object?
  • Was the angle of the jerking movement of your eye within 45 degrees?

This test supposedly indicates a BAC of .10 or higher 77 percent of the time.

What does the one-leg stand test look for?

In this test, you must hold up one leg approximately six inches off the ground for about 30 seconds while counting out the time. During this test, the officer looks for the following:

  • Did you have to hop to keep your balance?
  • Did you sway while attempting to maintain your balance?
  • Did you put your foot down prematurely?
  • Did you use your arms to maintain your balance?

The chances of your BAC being .10 or higher during this test is 65 percent. 

Those aren’t very good odds

If you don’t think that those odds are good enough, you aren’t alone. Even sober people fail the SFST far more often than anyone would like. In addition, any number of physical, medical or other circumstances can greatly affect the outcome of the test. If you believe some other factor influences your ability to adequately perform these tests, make sure the officer notes it in the report. You may need that information later if you face charges for DUI.

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