DUI Standardized Field Sobriety Testing

HGN Testing Explained

In conducting a HGN Test, the officer must look for five things in order
for the results of the tests to be validated by NHTSA standardization.

1. Equal Pupil Size Both Pupils must be of equal size;

2. Equal Tracking Both eyes must track the stylus (usually a pen or finger)together and equally.

3. Lack of Smooth Pursuit of the stylus by each eye

4. A distinct jerking (nystagmus) of each eye when gazing all the way to one side (Maximum Deviation)

5. Onset of nystagmus prior to maximum deviation

There are many causes of HGN besides alcohol consumption, including:

Inner ear problems
Strep Infections
Motion Sickness
Head Trauma
High Caffeine Intake
Antihistamine Use

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