This is the test where the officer holds up a penlight and moves it back and forth, asking the driver to follow the light with their eyes. This test is considered one of the more reliable field sobriety tests, yet not every state will acknowledge these tests in court. Read on to learn more about what the HGN test assesses, and how mistakes in this test could cost you dearly in a DUI or DWI case.

First of all, "nystagmus" is what happens when someone looks so far to the side they hit periphery vision: their eyes twitch. That twitch is called a nystagmus. A normal person's eyes would twitch when an officer holds out the light at a 45-degree angle to their eyes. When someone is intoxicated, however, their eyes will twitch before their eyes reach peripheral vision, when the light is at less than a 45-degree angle.

So the science behind the HGN test is real, not something as unreliable as counting back from 100 by sevens or other dubious DUI tests. According to the National Highway Traffic Safety Administration (NHTSA), these tests will be accurate if the officer giving the test has been trained in HGN testing.That being said, there are states where HGN tests cannot be used by a prosecutor to convict someone of driving under the influence. But these tests can be used in any state to justify an arrest.

So what is an officer looking for? These tests are not pass/fail, but a police officer is looking for any signs that someone could be impaired. There are three such signs:

• The eyes are jerking instead of smoothly going side to side.
• Once gazing as far to the side as one can, the eyes twitch.
• The eyes twitch before looking out at a 45-degree angle.

Despite being reliable tests in and of themselves, the fact remains that an officer can make an honest mistake, but a serious one that could land you a severe DUI charge. In order to overcome an HGN test, you would need to show that the officer did not perform the test correctly.

For instance, if the area was poorly lit and a driver's face is not entirely clear to the officer, then the test results can be dismissed by a court. This also means that someone taking an HGN test should take off their glasses, to ensure that the officer can plainly see their eyes and make no mistake. Also, the person taking the test cannot be looking in the direction of oncoming traffic. If headlights are flashing by them, this can cause eye twitches, which could be mistaken as a sign of impairment.

If you are faced with the possibilities of jail, fines, and other criminal penalties, you need to know how you can beat your charge and any tests in your case. Call a DUI lawyer today to learn what your available strategies are!