There are three field sobriety tests that are approved by the NHTSA. Known as the standardized field sobriety tests, they consist of the Horizontal Gaze Nystagmus (HGN) test, the walk-and-turn test, and the one-leg stand test. Today I will go over the HGN test.
Horizontal gaze nystagmus is essentially the involuntary jerking of the eye. For most people, this typically occurs at maximum deviation (that is, looking as far to the side as possible). However, nystagmus becomes more pronounced in those who are under the influence of alcohol.
Of the three standardized field sobriety tests, the HGN test is considered the most scientific, with an accuracy rate of 77% to 88% when administered correctly by the police officer.
To look for the nystagmus, the police officer will ask you to follow a small object, such as a pen or flashlight, with your eyes without moving your head. The officer is watching to see if you are able to smoothly follow the object with your eyes. He or she is also watching for distinct nystagmus when your eyes are at maximum deviation. The third thing that the officer is looking for is the onset of nystagmus before your eyes move to 45 degrees.
The officer is looking for three clues in each of your eyes for a total of six clues altogether. If the police officer believes that four clues were exhibited, you meet the arrest criteria.
Because it is known as the most scientific field sobriety test, the HGN has the most potential to be damaging if used in court. A good defense attorney must know how to attach the results during cross-examination.
There is one major flaw with the HGN test. There are over 100 different physical and medical problems that may cause nystagmus and are not related to alcohol. Poor vision and ocular blindness may cause nystagmus. Diabetes, brain tumors, and head traumas also lead to nystagmus. Since most police officers are not trained as ophthalmologists, it is almost impossible for them to say that nystagmus is caused by alcohol rather than another medical disorder.
Do you think that the HGN test is reliable enough to determine someone’s intoxication level?
