When you are pulled over for the suspicion of drunk driving, you might be asked to complete a field sobriety test. The standardized version of this test includes three components. One of the components is the horizontal gaze nystagmus test. This test uses the movements of your eyes to clue the officer conducting the test into whether you are intoxicated or not.
During this test, the officer will tell you to follow an object. This is usually a finger or an ink pen. While you are following the object, the officer is watching for abnormal, jerky twitches in your eyes as they track the object.
If the officer sees signs that you are intoxicated during the horizontal gaze nystagmus test, as well as the other components of the standardized field sobriety test, you might be asked to take a portable breath test. This test isn’t done for the purpose of evidence in court. Instead, it is performed to establish probable cause to initiate an arrest.
When you are arrested, you will have to take a more reliable blood alcohol concentration (BAC) test when you get the police station or at a hospital. This is what is used as evidence in the case that is presented to the court.
You must understand that all of the field sobriety test components and BAC testing come together to show the likelihood that you are intoxicated. You should pay attention to how these are conducted so that you can discuss this with your lawyer. There is a chance that you might remember something that proves valuable to your defense.
Source: FindLaw, “What Is Horizontal Gaze Nystagmus (HGN)?,” accessed May 12, 2017