Updated on November 14th, 2012 at 05:40 pm

The horizontal gaze nystagmus test is a field sobriety test that involves the officer examining the suspected drunk driver’s eyes for involuntary muscle jerking called nystagmus. The eyes of the driver are to follow a stimulus, and the police officer is supposed to look for smooth pursuit, nystagmus before a 45 degree angle, and nystagmus at maximum deviation. There is a procedure for the test; your Milwaukee DUI lawyer can explain to you in detail what any results of a field sobriety test mean for your case.

The first step is for the subject to remove any eyewear he or she might be wearing, including prescription glasses. Then, the subject is to put his or her feet together with hands at the sides, keeping his or her head still throughout the test. Then, the suspect is to look at the stimulus and follow its movement with his or her eyes only, without moving the head, until informed that the test is over. The stimulus is to be held about a foot from the subject’s nose and above eye level by the officer, who is to check for:

  • Equal tracking of the eyes.
  • Equal size in terms of the pupils of the eye.
  • Lack of smooth pursuit, by starting with the subject’s left eye and moving the stimulus at a speed where it takes two seconds to bring the eye as far to the side as it can go and two seconds for it to get back. Each eye should be checked in this way twice.
  • Distinct nystagmus at maximum deviation. As with checking for lack of smooth pursuit, the officer is to start with the left eye. Then, the officer should move the stimulus at a speed where it takes about two seconds to bring the eye as far to the side as it can go. This maximum position should be held for at least four seconds; this procedure should be repeated twice.
  • The onset of nystagmus prior to forty-five degrees. Beginning again with the left eye, the stimulus should be moved where it takes four seconds to reach the edge of the subject’s shoulder. The officer should stop and verify that the jerking continues when nystagmus is seen.
  • Vertical nystagmus, by holding the stimulus horizontally about foot in front of the suspect’s nose, just above eye level, then telling the subject to hold his or her head still and follow the object with his or her eyes, not head. Then, the officer is to raise to the stimulus until the eyes are raised as high as possible. This position is to be held for four seconds and checked for signs of jerking.


There are many types of field sobriety tests; the ones that are standardized must be performed in a consistent fashion. The experienced Milwaukee drunk driving attorneys at Vanden Heuvel & Dineen, S.C. can determine what other problematic aspects might cause your field sobriety test results to be considered invalid.