DWI Pen Test Accuracy
There are several field sobriety tests that an officer may conduct to determine whether you are under the influence of alcohol and/or drugs. These may include the horizontal gaze nystagmus test, the walk-and-turn test, and the one-leg stand test.Horizontal gaze nystagmus may be referred to as the “pen test,” because of the stimulus that is used to administer the test. Although considered the most accurate of the three field sobriety tests, this is not always the case.
Nystagmus is an involuntary jerking of the eye. This may occur when you look as far to the side as possible without moving your head. Experts say that the horizontal gaze nystagmus test is a good way to determine intoxication, as alcohol may affect your ability to control the eye muscles. The more intoxicated an individual is, the more pronounced the jerking becomes.
To administer the pen test, the officer will ask you to follow an object (usually a pen or penlight) with your eyes without moving your head. The pen is placed 12-15 inches from your face. The officer will look for several clues that may indicate impairment, such as inability to follow the object smoothly with your eyes, or the onset of nystagmus at 45 degrees.
However, there are other factors besides alcohol consumption that may cause nystagmus. These include eye strain, brain tumors, brain damage, and inner ear diseases. Because an officer is not a trained ophthalmologist or neurologist, it is almost impossible for him or her to determine the true cause of nystagmus.
If the officer was not properly trained on how to administer the pen test, or if he or she administered it incorrectly, this may also affect the results of the test. For example, if the officer puts the pen too close to your face, or moves the pen too quickly, the results may be inaccurate.
If you were arrested and charged with driving while intoxicated as the result of a failed pen test, it is in your best interest to contact a defense lawyer who focuses exclusively on DWI law. Your attorney will look at the DWI pen test accuracy to determine what arguments can be made against the results of the test.
