When police officers suspect people of drunk driving, they start looking for evidence. They ask a driver what they did previously to see if they may have committed a driving under the influence (DUI) infraction. They may ask them to exit the vehicle to submit to field sobriety testing.
There are three standard field sobriety tests, some of which make more immediate sense than others. The logic behind certain tests is relatively straightforward. Those under the influence of alcohol often struggle to walk properly or maintain their balance. Therefore, the walk-and-turn or one-leg stand tests make sense to most people.
However, another common test administered as a standardized field sobriety test leaves people a bit more confused. Police officers may ask drivers to follow a pen, a light or even their finger from side to side with their eyes without turning their heads. What is the point of having drivers move their eyes from side to side?
Alcohol strengthens involuntary muscle spasms
Field sobriety tests can easily produce false positive results. Tests looking at balance or walking ability can yield false positives if people have anxiety or a variety of different medical conditions. The horizontal gaze nystagmus test is less susceptible to producing false positives due to anxiety, although false positives are still possible.
Alcohol intensifies certain muscular functions. It is natural for the muscle that moves the eye to twitch or quiver slightly as people rotate their eyes from side to side. Those under the influence of alcohol tend to have much more pronounced movement.
The horizontal gaze nystagmus test looks at the intensity of the muscle spasm as a way of screening drivers for likely alcohol impairment. When combined with the two other field sobriety tests, the horizontal gaze nystagmus test can help a police officer affirm the likelihood of a driver’s intoxication.
Those who fail a horizontal gaze nystagmus test or other field sobriety tests may be at risk of arrest and prosecution. When the state’s case largely depends on field sobriety test results, that may influence the best defense strategy to use. Reviewing the state’s evidence with a skilled legal team can help drivers hoping to fight DUI charges develop the best strategy available.
