The most commonly used FSTs include the horizontal gaze nystagmus test, the walk-and-turn, and the one-leg stand. For the horizontal gaze test, an officer asks a driver to follow an object back and forth with his or her eyes. The walk-and-turn requires a driver to walk in a straight line toe to heel, and the one-leg stand, as the name suggests, requires the driver to hold one leg in the air while balancing on one foot.
Although these tests seem simple, they have faced sharp criticism from researchers and some DUI attorneys who question the tests’ ability to accurately determine intoxication. Criticisms are based mainly on a series of studies conducted by the National Highway Traffic Safety Administration (NHTSA). In one study, police officers incorrectly identified 47% of drivers as being drunk when they were in fact completely sober. In a later study, a professor at Clemson University, Dr. Spurgeon Cole, asked police officers to identify drunk drivers based on video footage of drivers performing field tests. The officers watching the videos incorrectly identified an individual as drunk nearly half the time. As a result, Dr. Cole concluded that the tests are highly subjective and unreliable. In an interview, Dr. Cole stated that the tests are “designed to fail. There are no norms, there is no average score. We have no idea what the average person could do on the one leg with the heel to toe.” According to Cole, even if officers perform all three tests together and do so correctly, “[y]ou are only 26 percent better than chance, 74 percent as much error as you would if you just randomly guessed.”
Moreover, others argue that a driver’s performance on the tests can be negatively impacted by many factors, including age, weight, shoe wear, and weather conditions. Some people who have underlying medical conditions, such as a condition impairing balance, may not be able to pass the tests even when sober.
I would love to hear your thoughts on this interesting and controversial subject! Please feel free to leave comments here , or questions so that I can respond.