You’re on your way home from dinner, and a police officer pulls you over. You were tired, so you may have drifted a little close to the centerline, but you certainly weren’t driving erratically. Just the same, the officer asks if you’ve been drinking, and you admit that you had a glass of wine earlier with your food.

Big mistake. The next thing you know, you’re being asked to step outside of the car while the officer performs roadside testing on you that is designed to ascertain your sobriety. When you fail it, you’re arrested — even though a Breathalyzer test shows that you’re well below the legal limit for intoxication.

One of the most commonly used roadside sobriety tests is called the horizontal gaze nystagmus (HGN) test — and it’s also one of the easiest to fail even when you’re stone-cold sober. It basically involves officers asking you to follow a small, moving object (like a pen or a penlight) with just your eyes while the officer watches. If your eye motions are smooth, you pass. If your eye motions are jerky or involuntarily jump around, that’s a sign that’s supposed to indicate you’re impaired by drugs or alcohol.

The problem with the HGN test is that it is deeply flawed. In ideal conditions, it can often indicate drug or alcohol intoxication, but being asked to perform the HGN at the side of the road, with police lights flashing and traffic passing by is hardly ideal. Plus, any number of common conditions can interfere with your ability to maintain a steady gaze on a moving object, including:

  • Fatigue or exhaustion
  • Allergies or dry eyes
  • Inner ear problems
  • Diabetic issues
  • Dizziness for other reasons
  • Anxiety
  • Brain injuries

In other cases, defendants “fail” the HGN test simply because the officer performing it is badly trained and doesn’t recognize normal eye motions.

If your drunk driving charge relates to a failed horizontal gaze nystagmus test, find out more about your options for a defense.