Drivers in Illinois facing possible DUI charges may go through a series of tests to determine if they are under the influence of alcohol, drugs or another substance. One of the common tests performed for this purpose is the nystagmus test. It's a type of test that assesses an individual based on involuntary eye movements. It's conducted by asking an individual to follow either a small flashlight or pen with their eyes as the object is moved back and forth in the front of the person's face from about 12 to 15 inches away, usually after being asked to step out of their vehicle.
Those who are stopped while driving on Illinois or other state roads could be asked to take a Breathalyzer test. Regardless of the result of the test, a person could be taken into custody and charged with drunk or impaired driving. It is important to note that the result of the test is not the sole piece of evidence that gets a person charged or convicted.
Illinois drivers who are stopped for suspected DUI typically undergo a field sobriety test. In fact, these types of tests are used by law enforcement officials in every state. One of the portions of this three-part assessment of driver capabilities is what's termed a horizontal gaze nystagmus (HGN) test. HGN refers to involuntary "jerky" eye movements that tend to become exaggerated while intoxicated.