Denver HGN Test for DUI Lawyer

Drunk Driving Defense Attorney in Colorado Springs, CO

The Horizontal Gaze Nystagmus (HGN) Test is widely regarded as the most reliable of the field sobriety tests developed by the NHTSA, and tests the reflexes of the eye. Nystagmus, or involuntary jerking, occurs naturally even when sober. When a subject is intoxicated, however, the jerking becomes much more pronounced and occurs under less extreme conditions.

In the HGN test, the police officer administrating the test will hold a pen or other visual stimulus approximately 12 inches from the subject’s face. The subject is then required to hold still and follow the stimulus with eyes alone as it is moved from side to side. The officer then scores the subject on a points system, with three points possible for each eye:

Failure to smoothly maintain focus on an object passing in front of it
Nystagmus becomes distinct when eyeball turns all the way to the side
Nystagmus begins before the eye turns 45º away from center

If the subject scores 4 points or higher, it is considered likely that he or she is under the influence of drugs or alcohol.

Our Denver DUI Lawyer Understands the Faults of HGN Tests

Unfortunately, while HGN tests are the most reliable, they are also the most difficult to administer and the easiest to influence by factors other than intoxication. Many health conditions have the potential to complicate test findings with false positives, as varied as:

Inner ear problems
Colorblindness
Epilepsy
Influenza
Streptococcal infection
Excessive caffeine consumption
Prescription barbiturate consumption
Antihistamine consumption
Eye fatigue

Dry, dusty weather and other eye irritations can also lead to false positives. Even if you were arrested on a DUI charge after failing an HGN test, skilled Denver drunk driving attorney can review your case and cast doubt on this field test as an accurate means of determining intoxication.