Understanding Standardized Field Sobriety Tests

Standardized Field Sobriety Tests (SFST’s) Clues

Field Sobriety Tests are a set of tests conducted by an officer when he suspects that a driver is impaired. There are three Standardized Field Sobriety Tests that have to be conducted by law enforcement in Wisconsin to detect the intoxication of a drunk driver.

Horizontal Gaze Nystagmus (HGN):

This test is designed to check the horizontal jerking of the eyes, which happens naturally when a person is intoxicated. The officer shows a stimulus in front of the person and asks them to track the stimulus with their eyes. The officer will mainly notice the following things:


  • Smooth Pursuit: The officer will notice whether the eyes move smoothly as he moves the stimulus, or are they jerking.
  • Distinct and Sustained Nystagmus at Maximum Deviation: When your eye reaches to the maximum deviation, it will automatically jerk – even in an unimpaired person. For a normal person, this jerk is very slight and not very noticeable. However, when a person is under the influence of intoxicant, the jerking is more pronounced and lasts for a longer period.
  • The Onset of Nystagmus Before 45 Degrees: A person is more likely to be impaired of his eyes start jerking at a deviation lesser than 45 degrees. The earlier it happens, the more intoxicated the person is.

The above mentioned clues are tested in both eyes, making a total of 6 checks. Officers are told that 4 out of these 6 clues is a sign of impairment.

Walk-and-Turn (WAT):

In most cases, this is the next test that an officer conducts. There are two phases of this test. In the first one, the driver is asked to stand in the starting position and demonstrate the verbal instructions given by the officer. In the next phase, the driver has to walk nine steps on a real or imaginary line, turn when told, and then walk nine steps back to where he started.

The officer will look for 8 clues:

  • Not maintaining balancewalk_the_line
  • Stopping while walking
  • Beginning before instruction
  • Stepping off the line
  • Not taking steps heel to toe
  • Wrong number of steps
  • Not turning properly
  • Using arms to balance

A 2 out of 8 proves impairment.

One-Leg Stand (OLS):

This is the last test, and also comprises of two phases. At first, the driver is asked to stand straight with arms by his side, and feet together. Next, upon the instructions of the officer, he has to lift his foot 6 inches above the ground. He has to keep the leg straight and the foot parallel to the ground. The driver is then instructed to count loudly from 1001 to 1030.

The four clues in this phase are:

  • Hopping
  • Swaying
  • Putting foot on ground
  • Using arms to balance

A 2 out of 4 will indicate impairment.  If you have been arrested for drinking and driving, or are in need of a criminal defense attorney, contact us today.