You have been pulled over and the officer suspects you have been drinking and driving. He orders you out of the vehicle and asks you to preform a series of field sobriety tests to determine if he should arrest you.

Horizontal Gaze Nystagmus or HGN is the eye test a police officer may ask you to preform during the Field Sobriety Test Battery to determine if you are driving under the influence of alcohol.

The HGN test was created by the National Highway Safety Traffic Administration and is designed to detect clues of alcohol consumption. It cannot determine the amount that was consumed although some believe that a blood alcohol estimate can be made.


Did I Pass the Horizontal Gaze Nystagmus test?

Many clients believe that they have passed the HGN eye test when in fact they have not. No, he is not testing your ability to follow his pen and keep your head straight.

Nystagmus is an involuntary jerking of the eye. Horizontal Gaze Nystagmus is the involuntary jerking of eyes moving laterally or side to side. There are many causes of Nystagmus; alcohol consumption is one of them, which is why it is used to detect drunk driving.

Click here for a video of an eye exhibiting signs of Horizontal Gaze Nystagmus

If you are exhibiting signs of consumption as the officer asks you to follow his pen or stimulus your eyes will not be able to smoothly purse the stimulus and will involuntarily jerk.

If your exhibit the clues nystagmus mentioned in the next section you did not pass the HGN test.


What the officer is looking for in HGN

The officer is looking for six “clues” of intoxication, three in each eye.

Lack of Smooth Pursuit – The officer moves the object from the center of the subject’s face towards their ear. The eye should smoothly follow the object, but if the eye exhibits nystagmus, the officer notes the clue. The officer then checks the other eye. This test is repeated.

Distinct Nystagmus at Maximum Deviation – Starting from the center of the suspect’s face, the officer moves the object toward the left, bringing the eye as far over as possible, and holds the object there for four seconds. The officer notes the clue if there is a distinct and sustained nystagmus at this point. The officer holds the object at maximum deviation for at least four seconds to ensure that quick movement of the object did not possibly cause the nystagmus.The officer then checks the right eye. This test is repeated.

Angle of Onset of Nystagmus Prior to Forty-Five Degrees – The officer moves the object at a speed that would take about four seconds for the object to reach the edge of the suspect’s left shoulder. The officer notes this clue if nystagmus begins prior to maximum deviation Forty-five degrees from center is at the point where the object is in front of the tip of the subject’s shoulder.


Michigan OWI Defense Lawyer

The majority of the time police officers run a suspect through the Horizontal Gaze Nystagmus test it is done incorrectly.

The National Highway Safety Traffic Administration mandates specific rules as to how the test is to be performed in order to accurately determine if a driver is under the influence of alcohol.

Officers often combine steps of the test or leave steps out to save time.

Officers often hold the stimulus too far or too close to the suspects face.

Officers often rush through the test and do not meet the timing requirements.

There are many medical and natural causes of nystagmus, possibly hundreds.

Optokinetic nystagmus is a common form of nystagmus that is often present while the officer is asking the driver to preform HGN. Optokinetic nystagmus occurs when the eyes fixate on an object that moves quickly out of sight or passes quickly through the field of vision. The flashing lights on the officer’s vehicle or passing traffic could cause this type of nystagmus.


What if HGN was done improperly?

The point of field sobriety tests is not to determine if you are safe to drive. The entire point of field sobriety testing is to determine if the officer has enough evidence to order you to submit to a preliminary breath test and / or arrest you for operating while intoxicated.

The HGN test is designed to build probable cause that a crime was committed and you probably committed it. If probable cause is present a search or arrest may be made. If probable cause is not present a search or arrest is a violation of your 4th Amendment and you cannot be searched or arrested.

If the test is preformed incorrectly and is the basis for the arrest or search of the suspect then the results of the search should be suppressed. Meaning that if the search of your breath or blood for alcohol was based on a poorly performed HGN test then the blood alcohol results should be suppressed.

If there is no blood alcohol in a drinking and driving case then your case should be dismissed.

Aaron J. Boria is a criminal defense lawyer in Michigan. Aaron handles a substantial amount of drinking and driving cases every year. Aaron has amassed hundreds of hours of continuing legal education and received a certification in the practitioner’s course of field sobriety testing. This makes Aaron a great lawyer for you and a dangerous lawyer against the prosecution and arresting officer.

If you have been charged with drinking and driving contact Plymouth defense lawyer Aaron J. Boria today (734) 453-7806

For more information on drinking and driving in Michigan click here.