What Is the Officer Looking For When the Officer Asks Me to Follow a Pen Light?

police officer

If you are ever stopped by a law enforcement officer in New York and the officer believes you were driving while intoxicated you will likely be put through a series of questions and asked to perform a series of field sobriety tests. During those field sobriety tests, or FST, you may be asked to follow a pen light. Understandably, you may wonder " What is the officer looking for when the officer asks me to follow a pen light? " A better understanding of the FSTs in general, and the horizontal gaze nystamus test specifically, should answer that question.

Once an officer becomes suspicious that a motorist has been driving while intoxicated, or DWI, the officer typically asks the driver to perform a series of FSTs to confirm the officer's suspicions. An officer may use just about any FST he or she wishes to use; however, most officers use what are referred to as the three "standardized" FSTs. They are considered "standardized" because they have been approved by the National Highway Transportation Safety Administration, or NHTSA. The three standardized tests include:

  • Walk and turn
  • One leg stand
  • Horizontal Gaze Nystagmus, or HGN

The walk and turn and one leg stand are aimed at testing a suspect's memory, balance, coordination, and ability to follow instructions. The results of these two tests are purely subjective, determined by the officer giving the tests. The HGN test is a bit more scientific, though the officer ultimately decides whether or not you passed this test as well.

Horizontal Gaze Nystagmus is a twitching or jerking of your eye that happens involuntarily when your eye moves to the side. If you try and look at something in your peripheral vision without moving your head, for example, your eye will eventually start to twitch a little. If you are intoxicated, however, the jerking or twitching will usually begin earlier and will be more exaggerated. Therefore, the HGN test is considered a good indicator of intoxication.

To test for HGN, an officer generally uses a pen light, though any similar instrument may be used. The officer will ask you to follow the pen light as it moves away from the middle of your field of vision and over to one side then back to the middle. Both sides are usually tested in this manner. The officer is looking to see when the twitching or jerking begins and how pronounced it is. The earlier the HGN begins and the more exaggerated it is the more likely the suspect is intoxicated.

If you have been charged with DWI or another alcohol or drug related driving offense, contact an experienced New York criminal defense attorney right away.