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Examples of False Positives for HGN Testing
Posted by: Michael Holmes
June 28, 2010
Topic: Understanding DUI & DWI
If you have 'failed' the NGH Roadside Sobriety Test, you may have actually only registered a false positive. How can you tell? I am glad you asked!
Even though this test is not a vision test per se, eyeglasses are to be removed in order for the officer to make a more accurate determination of the final total points. If the suspect can not see the stimulus after removing the eyeglasses, they must be allowed to perform the test with them on. According to the manual, hard contact lenses are to be removed so as to avoid dislodging when the eyes are out at maximum deviation or to prevent damage to the eyes. The manual says not to administer the test if the suspect is wearing hard contacts. A person with a glass eye or only vision in one eye can not be given this test.
At an accident scene, if the suspect sustains a concussion, this may bring on a pathological Nystagmus thereby invalidating this test.
As mentioned previously, colorblind individuals are not validated for this test.
If the officer believes that the Nystagmus might be present through non-drug or alcohol-related activities, the results can’t be scored. The benefit of the doubt must be given to the person that is being tested. The officer is also trained to administer this test with the suspect looking into a quiet background, away from police cruisers and other distracting activity. Otherwise, the individual being tested may produce a false positive due to an induced condition known as opto-kinetic Nystagmus. This is brought on when a person focuses on several objects at one time or objects that are moving away. The quiet background that is recommended is away from the view of passing motorists. This opto-kinetic Nystagmus is a defense mechanism of the body in order to keep the eyes from tiring. There are numerous visual or other distractions that may impede this test. Certain environmental factors such as wind, dust, etc. may interfere with the performance of the Nystagmus test.
In summary, the HGN test is just one of several tools that law enforcement are approved to use in order to ascertain sobriety. As I’ve explained, the administration of the test is very complex. Additionally, proper identification of Nystagmus as being directly correlatable to drugs or alcohol should require medical training. There are too many potential pre existing conditions and environmental variables at play.
If you have been charged with DUI or DWI and NGH testing was a component in your arrest, I strongly urge you to seek representation from a qualified Criminal Defense Attorney who can help build your case. An experienced Lawyer will know how to sort through all evidence related to the charges and aggressively defend your rights.
