How accurate are field sobriety tests?

Pennsylvania law enforcement officers are vigilant about making the city streets and highways safer. To this end, they are often on the lookout for signs of impaired driving. While these signs might include reckless driving, swerving, lane drifting or failure to recognize safety signs, there are only a few true tests to prove impairment.

Our state’s implied consent laws mean that a driver is presumed to consent to blood, urine or breath tests to indicate a blood alcohol content (BAC) level. Drivers do, however, have the right to decline to participate in a field sobriety test.

What are field sobriety tests, and are they reliable?

While there have historically been regional variations in testing, the National Highway Traffic Safety Administration (NHTSA) has developed standardized training for three field sobriety tests. Unfortunately, even with standardized training, the tests are still subjective measures of impairment:

• The walk-and-turn test: The officer will instruct the driver to take nine steps in a straight line, heel to toe, turn, and return along the same path following the same instructions. Numerous elements can impact a driver’s ability to perform these actions. The test might occur over uneven ground or pavement littered with road debris. The test might take place near passing vehicles which could break the driver’s concentration.
• The horizontal gaze nystagmus test: The officer will instruct the driver to watch their finger or the tip of a pen while it is moved up, down and side to side. The officer is looking for jerking or irregularity in the driver’s eye movements. Unfortunately, individuals might struggle with numerous medical conditions that affect eye control and the smoothness of movement.
• The one-leg stand test: The officer will instruct the driver to stand motionless and lift one foot six inches off the ground. This is a test of concentration and balance. Unfortunately, issues similar to the walk-and-turn test exist here. Uneven pavement, proximity to passing traffic and debris can all impact a driver’s balance. Additionally, an inner ear infection, uncomfortable shoes or a leg injury can cause a driver to fail this test.

Field sobriety tests, while standardized, are still a subjective measure of a driver’s impairment. It is crucial that drivers understand their rights during any type of traffic stop.