One of the most common questions I’m asked by lawyers is: how it is that I deal with the horizontal gaze nystagmus test evidence of a testimony at a motions hearing or in a trial in a Georgia DUI case? First, I believe there are several approaches/tactics that you may take at a motions hearing or in a trial. The tactics and objectives that you employ at a motions hearing challenging HGN evidence in a DUI case may be different from the tactics and strategies that we use in a jury trial for a DUI case. Second, I believe you have to have some overall understanding as to what it is the horizontal gaze nystagmus test -or HGN test- actually tells the officer, and what is it doesn’t tell the office.
Addressing HGN test in a DUI case in Georgia: HGN is not correlated to person’s ability to drive safely.
So many times, that we’re caught up, typically under Georgia law, in believing that the horizontal gaze nystagmus test can be correlated to a person’s actual driving ability, and that has never been the case. There is no validation of the HGN the test whatsoever to predict your client’s ability to drive safely.
The only thing that the horizontal gaze nystagmus test has ever been shown to do is – to some varying degree of probability – predict a person’s blood alcohol concentration. And it’s not very good at that. If any of you have you have ever been through a field sobriety training course, you recognize that HGN is actually really difficult to see. And it certainly doesn’t affect a person’s ability to see as they’re driving. So, what I have developed with a police officers through cross examination typically, is just very simply, you can’t correlate a person’s presence of HGN in the person’s eyes to their ability to drive safely. And that is in fact the reason that we are there in a less safe case – is that they’re alleging that your client had an impaired ability to drive safely as a result of alcohol or drugs.