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Grant M. Scheiner - Houston Criminal Defense Lawyer

Understanding the Horizontal Gaze Nystagmus Test in Texas DWI Investigations

If you are pulled over for on suspicion of DWI, DUI or any alcohol related offense in Houston, Texas or anywhere, it is likely that you were subjected to sobriety tests known as Standardized Field Sobriety Tests (“SFSTs”). A good criminal defense attorney will be familiar with the three SFSTs  employed by law enforcement in DUI or DWI investigations – the horizontal gaze nystagmus test (known and “HGN” or simply the “eye test”), the walk and turn, and the one-leg stand.

Criminal defense lawyers know that the first test officers conduct is the HGN test. Using an object like a pen, a small flashlight, or even just a finger, a police officer will ask a DWI or DUI suspect to follow the tip of the object with their eyes, and their eyes only. The officer will then look at each eye individually and look for an involuntary jerking of the eyes as they follow the object.

Law enforcement in Texas and elsewhere claim that in DWI or DUI investigations, the HGN test is the most reliable SFST. They claim that as a person’s blood alcohol increases, it is more likely that the involuntary jerking of the eye will be present.

Criminal defense lawyers who understand the science behind these tests and the way they are administered are highly skeptical of their reliability. Even if someone’s eyes are displaying involuntary jerking there may be other reasons for the jerking other than consumption of alcohol. Additionally, criminal defense attorneys know that a surprising number of officers in Texas do not follow the standardized guidelines for administering the HGN test in DUI or DWI investigations.

A good criminal defense attorney should be familiar with the guidelines and be prepared to challenge the HGN test in your DUI or DWI case.