Answer: Sure. The first one is called the horizontal gaze nystagmus. What that means is that the officer is looking for an involuntary jerking of the eye caused by alcohol, which is the central nervous systems depresent. There are hundreds of substances or hundreds of other types of ways or reasons why your eyes may move or jerk in an increased or enhanced fashion. It’s not solely due to alcohol. However, the way that works is that officers are trained by other police officers. If they move their finger in a certain fashion, and they take the correct number of passes in a correct number of seconds, they can try to make the determination if the person is under the influence of alcohol. The HGN does not necessarily tell you if someone is impaired, but it can give you estimation if their alcohol level is above or below .08 grams or more. What they’re looking for is six different things. They’re looking for whether your eyes pursue smoothly, they’re looking for whether you have a jerking at maximum deviation, which is where you see nothing but the whites of someone’s eyes, they’re looking for lastly onset of nystagmus, where your eyes start jerking before 45 degrees, which is generally between the shoulder lines when the officer moves his finger outside of the shoulder.
The second test is the walk and turn test, where they’re looking for 8 different things. They’re looking to see if you can stand with your right foot properly in front of your left foot, if you start too soon, if you take an incorrect number of steps, if you stop walking during the course of the test, if you take improper turns, if you start the test too soon, if you raise your arms beyond six inches, if you don’t touch heel to toe. There are eight clues that they’re looking for, and if you show or exhibit two of those clues, the officers can try and determine that your alcohol level would be at a certain impairing level. However, most people have a difficult time doing that. The test is not necessarily designed to p ass. It is very difficult to do whether you’ve been drinking or not drinking.
Lastly the one leg stand is the officer looking for four things, for four clues. He’s looking first to see if you hop, sway, put your foot down or raise your arms beyond six inches from your side. If you exhibit two or more of those clues, the officers are trained to believe that you are impaired pursuant to the National Highway Traffic Safety Administration or NHTSA, their rules.