Nystagmus

The National Highway Traffic Safety Administration studied several field sobriety tests and found that three showed some scientific validity as indicators of a test subject’s blood alcohol content. These three tests, called “standardized” field sobriety tests, are now the most commonly administered in Orange County drunk driving arrests. They are the walk-and-turn test, the one-leg stand test, and the horizontal gaze nystagmus test.

What Is Horizontal Gaze Nystagmus?

Horizontal gaze nystagmus is a back-and-forth oscillation of the eye. It is involuntary, and the person exhibiting it is not even aware it is happening. It is caused by a disturbance of the inner ear or the oculomotor system.

What Signs Will Police Look For?

Though it is used by the police as an indicator of intoxication, horizontal gaze nystagmus occurs naturally in everyone to some degree, regardless of whether or not they are intoxicated. The police will look for three signs when testing you for horizontal gaze nystagmus:

- Lack of smooth pursuit

- Distinct and sustained nystagmus at maximum deviation

- Onset of nystagmus prior to 45 degrees

The test will be performed twice, making a total of six clues the police officer will look for. The presence of four or more of these clues will lead the officer to conclude that your blood alcohol content is greater than 0.10 percent.

Is the Horizontal Gaze Nystagmus Test Reliable?

The horizontal gaze nystagmus test and the other two standardized field sobriety tests are generally more reliable than the myriad other tests police officers sometimes perform. However, any Orange County drunk driving attorney will tell you that there are still certain problems inherent in the test. Police officers are warned that nystagmus may be present due to causes other than alcohol intoxication. Nicotine, caffeine, aspirin, and certain medications can cause nystagmus, as can eye irritants or visual distractions like strobe lights or passing traffic.

How Can an Orange County Drunk Driving Lawyer Help?

Juries tend to trust “scientific” evidence, and if you performed poorly on a horizontal gaze nystagmus test, the prosecutor is likely to tout the test’s validity and reliability. An experienced Orange County drunk driving lawyer will be able to overcome this impression and expose the test’s shortcomings through skilled cross-examination. If you have been arrested for drunk driving in Orange County, please call Tom Wallen at (888) 444-7210 to schedule a free case evaluation.