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Horizontal gaze nystagmus as a sign of impairment

When a Florida driver is stopped for suspicion of drunk driving, one of the field sobriety tests that is commonly conducted tests for horizontal gaze nystagmus, or involuntary jerking of the eyes. This jerking can become more exaggerated when alcohol is consumed. As such, it can often be used as evidence that the driver was impaired when he or she was stopped.

Essentially, the consumption of alcohol causes a person’s natural eye movement to become more pronounced, particularly in sideways eye movements, as it depresses the person’s nervous system. In most cases, those who exhibit nystagmus may not even be aware that their eyes are moving in a jerky manner as it does not have any effect on their vision. When combined with the one-leg-stand test and the walk-and-turn test, HGN tests can help accurately determine if drivers have a blood alcohol concentration that is at least .10 percent in the majority of all cases.

The HGN test is considered to be scientific and reliable by most courts. However, the results of the test can be challenged and thrown out if it can be shown that the test was not properly conducted to the standards set by the National Highway Traffic Safety Administration. It should also be noted that the evidence could be thrown out if the accused person can demonstrate that eye strain, brain damage or neural activity resulted in the nystagmus.

The state of Florida is known for its tough drunk driving laws. If a person is accused of drunk driving after being pulled over, he or she could face fines, a loss of his or her driving privileges and even jail time. A DUI defense attorney may work to have some or all of the evidence that was collected thrown out if it can be shown that the evidence of impairment was not collected or documented according to the standards.