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Understanding HGN Tests in Portland

Police who have pulled you over in Portland are supposed to have reasonable suspicion that a crime or traffic infraction has been committed. During the traffic stop, be prepared when the police also try to find evidence of a more severe violation like operating under the influence (OUI).

One method they use to gather evidence of an OUI is a field sobriety test, like the Horizontal Gaze Nystagmus Test.

The Role of Field Sobriety Tests in OUI Law

In general, field sobriety tests are an evidence-gathering method law enforcement personnel use to find evidence of an OUI that can be admissible in a Maine court.

In Maine, not just any field sobriety test can be used though: the test must be approved for use by the National Highway Traffic Safety Administration (NHTSA). The NHTSA has long recognized three field sobriety tests as adequate for detecting drunk driving:

  1. The Horizontal Gaze Nystagmus Test
  2. The One Leg Stand
  3. The Walk-and-Turn.

Each of these tests has a “one-way” result: If you take the test and fail it, you will get arrested and will have provided valuable evidence for prosecutors to pursue OUI charges. If you pass a field sobriety test, on the other hand, it means nothing – police can continue to question you and have you perform other field sobriety tests until they find evidence that you are under the influence of alcohol or drugs.

The Horizontal Gaze Nystagmus Test

The Horizontal Gaze Nystagmus Test is one of the easiest and the least physically demanding field sobriety test that can be done in Maine. It looks for “nystagmus,” or an involuntary shaking, of your eye that is caused by alcohol – though there are also other causes for the involuntary movement.

Once you are out of your vehicle, the police officer will stand a few feet in front of you and hold up a finger or a pen. The officer will tell you to keep your head still while he or she slowly moves the finger or pen from one side to the other.

The Nystagmus Test is performed on one eye at a time, starting with your left eye. The officer will move the target back and forth across your range of vision twice before switching to your right eye. At the point of maximum deviation – where your eye is looking as far to the side as it can – the officer will pause the target and closely watch your eyeball for nystagmus. If the officer sees nystagmus in your eye before you have reached a 45-degree angle, it can be used as a sign of a high level of blood alcohol concentration (BAC).

Officers conducting a Horizontal Gaze Nystagmus Test look for three clues in each eye:

  1. the eye's inability to smoothly follow the target;
  2. nystagmus at the point of maximum deviation that is sustained for at least four seconds; and 
  3. the onset of nystagmus in the eye before the eye has looked more than 45 degrees to the side.

Because there are three clues for each eye, there are a total of six potential areas of "failure" in the Horizontal Gaze Nystagmus Test. If you score four or more points, you will have failed the test and be arrested for OUI.

Inaccuracies in the Horizontal Gaze Nystagmus Test

The Horizontal Gaze Nystagmus Test was approved by the NHTSA in 1981 when the legal BAC limit was 0.10%, making it an antiquated relic of OUI law.

Beyond that, though, the very studies that the NHTSA relied on to approve the Horizontal Gaze Nystagmus Test have shown that it is woefully inaccurate. Even though the NHTSA's studies were conducted in a lab with no distractions, they still found that the Horizontal Gaze Nystagmus Test was only accurate 77% of the time. Because nystagmus is more pronounced when an OUI suspect's BAC is higher and because the NHTSA's studies were done when the legal limit was 0.10%, the accuracy of the Horizontal Gaze Nystagmus Test is going to be far lower with the lower BAC limit.

What this means: at least one out of every four people who fail the Horizontal Gaze Nystagmus Test is not intoxicated.

In the field, the test's accuracy is even worse. Distractions behind the target, including traffic, can make it difficult for a suspect to smoothly follow the target. Additionally, there are plenty of things that can cause nystagmus that have nothing to do with alcohol:

  • Contact lenses;
  • Eyeglasses;
  • Head injuries; and
  • Medications, especially for seizures.

How the Nystagmus Test Can Be Manipulated

When properly done, the Horizontal Gaze Nystagmus Test is far from precise. When improperly done, it is even worse.

Police can purposely or mistakenly skew the results of the Horizontal Gaze Nystagmus Test in the following ways by:

  • moving the target back and forth in a jerky or unsteady way, preventing you from “smoothly tracking” it and scoring points against you in the test even though you are doing it properly;
  • positioning traffic, flashing lights, or other distractions behind the target to induce eye movements that could be attributed to nystagmus; or 
  • mistaking what amounts to a 45-degree angle and scoring points for “early onset nystagmus”.

Even when perfectly administered, police can misinterpret or “imagine” nystagmus in an OUI suspect. Nystagmus is a tiny movement in the eye that can easily be “seen” by people who want to see it. Especially when the Horizontal Gaze Nystagmus Test is conducted in a poorly-lit area, it is very possible for police to detect nystagmus where none is present.

Portland OUI-Defense Lawyers at the WTB Law Office

If you have been arrested and charged with OUI after failing a field sobriety test, including the Horizontal Gaze Nystagmus Test, you need legal help. The OUI-defense lawyers at WTB Law in Portland, Maine, represent people accused of drunk driving or drugged driving throughout the region. Contact us online or call our law office at (207) 571-8146 for the legal help and representation you need.

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