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What purpose does the horizontal gaze nystagmus have?

On Behalf of | Aug 14, 2015 | Field Sobriety Tests |

If you’ve ever watched a police procedural show involving a suspected drunk driver or have been pulled over yourself in real life, chances are you’ve seen an officer shine a flashlight on an individual and then asked them to follow the movement of a pen or finger. If you’re like some of our Denver readers, you might not know why officers do this or what it has to do with determining intoxication.

Because this test is so widely used across Colorado and the nation, we thought it’d be a good idea to take a look at the science behind the horizontal gaze nystagmus test in order to see why officers use it during field sobriety tests.

As you may or may not know, movement of the human eye is controlled by the vestibular system. When there is a disturbance in this system, nystagmus can occur, which is the “involuntary jerking or bouncing of the eyeball.” According to the National Highway Traffic Safety Administration, alcohol can cause just such a disturbance, hindering muscle control of the eye and causing nystagmus. The more intoxicated an individual is, the more pronounced nystagmus becomes.

Some trial courts in the country do not allow nystagmus test results to be admitted into evidence for DUI trials because improper training and a lack of scientific knowledge can cause evidence to fail the evidentiary standards needed for a conviction. This may not necessarily be the case though in Colorado where the nystagmus test is one of the main standard field sobriety tests given during a DUI stop.

Despite the fact that protecting your rights during a DUI stop is incredibly important, most people are unaware of how to do this. By contacting a skilled criminal defense attorney, you will not only learn how to protect your rights but effectively do so during the rest of a criminal investigation. This may not necessarily be possible though without a lawyer’s help, which is something all of today’s readers should keep in mind.