The "eye test" is a common field sobriety test that is conducted by law enforcement during DUI stops in Illinois. The official name of the test is the Horizontal Gaze Nystagmus (HGN). If the officer has any suspicion that you may have been drinking, he will usually conduct an HGN test. However, the test has many different steps and specific procedures. If the test is not performed exactly as standardized, or if the officer combines steps, omit portions of the exam or perform the test too quickly, the results may be invalid.
There are several different versions of the HGN test. These include observing your eye movement patterns with use of a stimulus held about twelve inches from your face and moving the stimulus:
- From side to side;
- Up and down;
- Around the eyes; and
- Toward the eyes.
Typically, you will be instructed to stand with both feet together and your hands at your sides. The test should begin with the officer checking the eyes for equal pupil size and equal tracking. This step can reveal medical conditions that cause Nystagmus, which is defined as rapid involuntary movements of the eyes. However, many officers skip this critical first step, thereby invalidating the results before the test has even begun....