In defending charges of DUI in Massachusetts, one of the field sobriety tests that appears frequently in police reports and causes the most confusion for people arrested for drunk driving is the Horizontal Gaze and nystagmus field sobriety test, sometimes referred to by those arrested as the pen test.
It is understandable why this test causes some much confusion because it does not appear to have an scientific basis or reliability. You are on the side of the road, cars going by, and the officer is waiving a pen quickly in front of your face. If you stopped and asked most officers what they are looking for, many probably could not correctly explain the correct procedure in administering the test.
Fortunately, the HGN test is typically not admitted into evidence at a Massachusetts DUI trial as a result of the decision of the Massachusetts Supreme Judicial Court in Commonwealth v. Sands. The HGN test can be admitted; however most prosecutors do not attempt to admit the test into evidence.
In some cases, I have used the HGN test to discredit the officer and demonstrate that the investigation was not properly conducted, so what are the signs that someone exhibits nystagmus.
The first clue that the officer looks for is lack of smooth pursuit. The officer is suppose to start with the pen in the center and move it to the left, taking two seconds out and two seconds back for a complete pass and following the same procedure for the right eye. The idea is that the officer is looking to detect any involuntary jerking of the eye, called nystagmus of which alcohol is one of many causes. Click here to read about court decisions regarding the HGN test.
The second clue is referred to as distinct and sustained nystagmus at maximum deviation. For this clue, the officer is suppose to move the pen until the eye has gone as far to the side as possible. The officer is then required to hold the pen in this position for a minimum of four seconds and observe to determine if there is an involuntary jerking of the eye. In many cases, the officer does not recall that the correct administration of this part of the test requires that the pen be held for four seconds at maximum deviation.
The final clue on the HGN test is called onset of nystagmus prior to 45 degrees. The officer is suppose to start with the stimulus in the middle and move it toward the right shoulder at a speed that would take four seconds to reach the edge of the left shoulder. In many cases, when officer perform this test, they are rapidly moving the stimulus contrary to the clear instruction of the police training manual.
With this clue, the officer is looking to see if there is any involuntary jerking of the eye prior to 45 degrees and is suppose to hold the stimulus to verify that it continues.
Although this test is rarely used in Massachusetts, according to the National Highway Traffic Safety Administration Study, the HGN test is the most accurate of the field sobriety tests at 77% reliable, as compared to 68% for the nine step walk and turn and 65% for the one leg stand. The head Police officer for the Massachusetts State police who speaks occasionally at drunk driving seminars for lawyers has repeatedly indicated his confidence in the reliability of the test. I have had an officer testify that he has never had a suspect fail the HGN test who was under the legal limit. During that hearing, the officer demonstrated how he conducts the test and did it in a very rapid fashion contrary to the careful and deliberate process outlined in the police manual.