After being stopped by a police officer, sheriff or even a state police officer you are asked to submit to certain tests because the officer believes you may be intoxicated, you should understand what these tests are and what they really look for. As explained by FieldSobrietyTests.org, none of the three standardized tests used in a drunk driving investigation can or are even designed to prove that you are intoxicated.
Field sobriety tests are used to collect just enough evidence to show that you might be intoxicated so that an officer can legally place you under arrest and charge you with a drunk driving crime. Of the three tests approved by the National Highway Traffic Safety Administration, one is called the horizontal gaze nystagmus test. It is the most accurate of all three but even so its accuracy rating is only 77 percent.
A nystagmus is a naturally occurring jerking of the eye that is said to be more pronounced if you have alcohol in your system. An officer will move an object and require you to follow it with your eyes from one side to the other. When and how obvious the jerking motion appears may contribute to the determination of your passing or failing this test. Some medical conditions may interfere with your ability to pass this test.
If you would like to learn more about the horizontal gaze nystagmus test and the other elements involved in a drunk driving investigation, please feel free to visit the drunk driving charges page of our Pennsylvania criminal defense website.