The Horizontal Gaze Nystagmus Test

Why Is This Test Used By Police Officers In Houston?

As you may know, law enforcement officers throughout the United States have been trained to detect certain indications of drunkenness. While some signs may seem obvious, like slurred speech and impaired motor function, others are much more subtle.


For this reason, the National Highway Traffic Safety Administration has developed a number of “standardized” field sobriety tests for law enforcement officers to utilize in the field. Most of these tests have been designed to assess a driver’s cognitive and physical abilities, since both can be impaired by the effects of alcohol, but one in particular addresses a more specific symptom of intoxication: horizontal gaze nystagmus.


Horizontal gaze nystagmus is an involuntary movement of the eye, which can be caused by a number of different factors, one of them being the consumption of alcohol. Instead of tracking movement in a smooth or uninterrupted manner, the eye will involuntarily jerk or twitch as it moves from side to side. For this reason, law enforcement officers frequently use the horizontal gaze nystagmus test when conducting a roadside DWI investigation.


According to studies, this type of field DWI test has proven to be more accurate than some of its counterparts (i.e., the walk and turn or the one-leg stand), so law enforcement officers have been trained to look for the following indicators:

  • Lack of smooth or fluid eye movement
  • Distinct jerking at maximum deviation
  • Onset of nystagmus prior to 45 degrees

Can a Failed Field Sobriety Test Be Used Against Me At Trial?

In many cases, the prosecution will use whatever evidence they can to convict a defendant of DWI. For this reason, they may bring up the fact that you failed a preliminary sobriety test. Unlike breath or blood tests, however, field sobriety tests are entirely subjective. Simply put, it is up to the arresting officer to decide whether or not a slight jerk in the suspect’s eye is an indication of intoxication.

That being said, it may be easy for your Houston DWI lawyer to have this evidence thrown out before a jury ever sees it. There is no way that a horizontal gaze nystagmus test can offer a scientifically accurate depiction of your blood-alcohol concentration, so you should not hesitate to fight back with the help of Jim Medley & Associates.

Why You Should Have Jim Medley On Your Case

Jim Medley, a veteran defense attorney serving the Houston region, is an expert in the field of DWI law. Not only does he hold a master’s degree in forensic toxicology, but he has also published numerous articles on field sobriety testing and personally trained police officers on DWI testing procedures. For this reason, you can trust that you he will provide nothing short of the skilled legal representation that you will need to effectively fight your drunk driving charges. When faced with legal penalties that include jail time, fines and the suspension of your driver’s license, you will want an experienced criminal lawyer like Medley in your corner. Call our office today to find out how he can help.

Call Jim Medley & Associates Today for a Free Case Evaluation

If you were arrested for DWI after failing a field sobriety test, the legal team at Jim Medley & Associates P.C. would like to hear from you. Their team is knowledgeable in all aspects of criminal defense, and will work tirelessly and vigilantly to defend you.

Call 713-893-0908 today or submit a free case evaluation form online.