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Interviewer: How is the horizontal gaze nystagmus test performed and what's the purpose of that particular test?

Kevin Roach: First of all, before administering the HGN test, the police officer is supposed to check your eyes for possible impairments. After he checks for possible impairments, next, the officer is supposed to check your eyes and make sure the pupils equally contract and are the same in size. The officer is also supposed to check for other problems with your eyes. If the driver is deemed eligible to take the HGN test, the officer is then supposed to proceed with the test.

Very rarely do you see an officer detecting any kind of impairment. Usually the officers are not thoroughly trained and don’t bother to take the time to check for eye issues and just go ahead with the test.  Regardless, they are supposed to check for impairments, medical conditions, et cetera with the eyes before even starting the test.

After starting the HGN test, the test is supposed to measure the involuntary jerking in the eye with three clues. The three clues they're supposed to look for are lack of smooth pursuit, distinct nystagmus at maximum deviation, and the last one is an onset of the nystagmus prior to 45 degrees. Each of these clues are distinct steps that must be tested by the officer in order for the HGN test to be valid.

People, when they’re reading this, must wonder, “What the heck does that mean?” A lot of the officers don't know what it means either. They had to be properly trained in how to administer this test or else it is invalid. I typically see that officers incorrectly administer the test by moving their finger either really fast or really slow making it impossible to properly show if there is the jerking motion.

It is Possible That the Police Officer May Not Perform This Test Correctly

Interviewer: Is this performed while the individual is sitting or standing?

Kevin Roach: Typically, it's done when they're standing.

Interviewer: Do you think it helps sometimes, when someone hires an attorney who knows about the different municipalities, judges, and things like that? Do you think that's an advantage to them?

Kevin Roach: Absolutely. When you're familiar with DUI arrests in the St. Louis area as well as the specific police department you're dealing with, you can really size up the quality of the case that they are going to have against your client.  You’ll have a good idea whether they're going to do all the right paperwork, whether they're going to observe your client for 15 minutes like they are supposed to before administering the test, whether they're going to give your client the proper implied consent, etc. With there being so many detailed mandatory procedures involved in a DWI arrest, you can pretty much assume that when it comes to a lot of these smaller municipalities, there is a high probability that they're not going to do everything correctly.

On the other hand, when you're dealing with municipalities where they have a lot of DUI’s, like St. Louis County or St. Charles County, you can pretty much bank on their officers doing everything by-the-book because they do so many of these and they are challenged on these cases on a regular basis. Their officers are pretty well versed on what procedures they need to follow.

Contact a St. Louis DWI Defense Lawyer Today

Kevin J. roach is a St. Louis DWI defense attorney who has defended thousands of DWI and DUI cases in the St. Louis Metro area. Call us today at (636) 519-0085 or (866) 519-0085 for your Free Consultation!

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