While I strive to give you an accurate and applicable answer to your question, and if I can possibly provide a legal avenue for you to have a successful legal outcome I will, I don’t have the ability to provide you with favorable law if it doesn't exist. As you read my answer to your question, I ask you to please don't shoot the messenger.
I'm afraid that you are on the wrong track in believing that by attacking the efficacy of the HGN (nystigmas test) in the presence of oncoming traffic is what is known as a red hearring. Even if you show that in your circumstance the test was administered in a faulty manner, it will not effect your case.
The test is based on the fact that alcohol affects the automatic tracking mechanisms of the eyes. Nystagmus is defined as "an involuntary rapid movement of the eyeball, which may be horizontal, vertical, rotatory, or mixed." Alcohol slows down the eyes' ability to rapidly track objects and causes to eyes to oscillate, or "jerk", before they normally would in a sober person. Alcohol stimulates the nerve endings, making nystagmus more pronounced in intoxicated persons. As a person's blood alcohol concentration increases, the eyes will "jerk" sooner as they move to the side.
A positive nystigmas test by itself is insufficient to prove you are under the influence. That fact would be proved with other tests as well--typically blood, breath or urine.
Here is a good site to learn about the HGN test:
If your situation is such that you are being charged with a crime based SOLELY on an HGN test, let me know and we can discuss this further. However, having the HGN test alone put in douby will not serve as a workable defense to driving under the influence and similar such allegations.
I wish you well.
Hello Doug: Thank you for the answer. All they have is the HGN and I did notice
in the NHTSA that in order to use this in Court that the police can not deviate
from normal procedure. I found in there that they should never place defendant
toward passing traffic and that they MUST follow proper procedure as in NHTSA
manual. Does same test indicate alcohol and drugs. HOW MANY clues are
possible on the HGN.
Do you think there would be case law where this mistake by police has been
Hello Again Doug:
they did not have probably cause. I had a minor accident ( no damage to either car)
in parking lot of business. Before we leave this discussion could you answer how
many clues are possible in HGN test and if test for Alcohol is same as
test for Drugs. Thanks so much. j
Here is a quote from the site I provide you a link to: XXXXX XXXXX: Alcohol and Nystagmus:
“There are several types of nystagmus. Alcohol causes two types: alcohol gaze nystagmus, which includes HGN, and positional alcohol nystagmus. Although alcohol causes both, alcohol gaze nystagmus and positional alcohol nystagmus are very different and easily distinguishable. Testing for positional alcohol nystagmus is not a part of the standardized field sobriety test battery. Defendants sometimes claim or attempt to confuse matters by arguing that the nystagmus the officer saw was actually positional alcohol nystagmus and not alcohol gaze nystagmus.”
Nystagmus tests can be used for some drugs as well and the results are the same as with alcohol.
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