Atascosa County Texas DWI Law : HGN Field Sobriety Test

In our last blog entry, we discussed some ways to attack the validity of the Horizontal Gaze Nystagmus (HGN) test.
During a jury trial, the jury will review the video, but it is highly unlikely that they can pick up the subtle bounce or nystagmus of the eye from the video. They are essentially relying on the officer’s testimony that he witnessed clues of intoxication related to nystagmus. A jury will be extremely doubtful of the officer’s observations, if a Bexar County DWI attorney can demonstrate that the officer has written reports with mistakes, that his testimony differs from the video, and that he did not perform the HGN test according to NHSTA specifications.

An especially strong tactic is when the officer claims that the driver was swaying and unable to stand steadily. Well, the inevitable question when an officer testifies like this, is how on earth he could possibly estimate a 45 degree angle for onset of nystagmus if the driver is swaying? The officer will either claim he could detect the nystagmus before a 45 degree angle was reached on a person moving back and forth or that somehow the driver was able to stand still throughout the HGN field sobriety test. The officer will inevitably contradict himself and the jury will cast doubt on his credibility. Any swaying during the HGN will ultimately render the HGN test invalid. If the officer contends the driver was swaying but then remained still during the HGN test, the jury will question whether in fact the driver was intoxicated if he was able to stay still during the entire administration of the HGN test.


Another key weakness of the HGN test brought out by the DWI video is that very rarely does the driver give his permission for the officer to do the test. Nor does the officer ever ask the driver. The officer will ask innocently if he can check the driver’s eyes without telling the driver that he is in fact administering a field sobriety test. Ultimately, a driver has the right to refuse any and all field sobriety tests, and jurors will interpret the officer’s actions as being underhanded and unfair.

The NHSTS had indicated that nystagmus is not necessarily a product of intoxication and can in fact be attributed inner ear infections, brain tumors and brain damage. More likely than not, the officer will not take the time to see if the driver may have had any of these conditions. Nystagmus is attributable to many different factors, and it does not follow that intoxication must have been what caused the eye to bounce. A Wilson County DWI attorney can effectively cross-examine an officer on the HGN test and negate any inferences of intoxication.

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