State Standardized Field Sobriety Tests

Though there are many field sobriety tests, the National Highway Traffic Safety Administration (NHTSA) has standardized three. They are the Horizontal Gaze Nystagmus (HGN), the One Leg Stand and the Walk and Turn. The tests are designed to assist police officers in determining whether or not a person is intoxicated, however these tests are not considered scientific evidence.

The HGN

In this type of test, a police officer will ask the driver to follow a stimulus, which is usually a pen with a light. The officer will be looking for a nystagmus—an involuntary jerking of the eyes as they gaze to the sides. Alcohol is thought to cause nystagmus. One of the flaws with the test is that it can be difficult for an officer to recognize—after all, they are not trained ophthalmologists.

The One Leg Stand

If you’ve ever driven past a person hopping up and down on one leg on the side of the road, they’re taking the One Leg Stand field sobriety test. The officer is really looking for two things: the ability for the driver to follow instructions and the ability for the driver to complete the tasks. The driver will be asked to raise one leg six inches off the ground while keeping their arms at their sides. They must point their toe out and count out loud to 30. If the officer notices the person swaying or losing balance, it’s a sign that the person is intoxicated.

The Walk and Turn

Similar to the One Leg Stand, the Walk and Turn is also a divided attention test. This means that the officer wants the person to follow the instructions then perform the test as expected. The driver is required to take nine heel-to-toe steps along a line on the side of the road. They must then turn and walk back taking the same nine steps, all while counting the steps out loud.

The issues with both the One Leg Stand and the Walk and Turn are that they both require physical abilities that some people who are sober cannot even perform. The officer must ensure that they are taking these tests on a hard, flat, non-slippery surface.