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Are Field Sobriety Tests as Accurate as Statistics Indicate?

The U.S. National Highway Traffic Safety Administration’s (NHTSA) information on field sobriety testing covers the use of three separate tests, known as “standardized” field sobriety tests: the horizontal gaze nystagmus test, the walk and turn test, and the one-leg stand test. NHTSA cites statistics from multiple studies to support the claim that these tests are highly accurate when it comes to accurately identifying drivers whose blood alcohol concentration, or BAC, is above the legal limit of 0.08 percent, or who are too impaired by alcohol or other drugs to drive a car safely. But are the tests as uniformly reliable as these statistics seem to claim?

At first glance, the numbers look good: NHTSA cites a 1981 study that concluded the three field sobriety tests, when used together, were 81 percent accurate in identifying people impaired by alcohol or drugs. A 1998 study also cited by NHTSA brought these numbers up to 91 percent overall, claiming that better officer training had made the tests more accurate. Even if these numbers are accurate, however, they still indicate that 10 to 20 percent of drivers arrested for drunk driving were not too impaired to legally drive a vehicle.

Breaking down the “overall” percentages, however, paints a different picture. For instance, the 81 percent “œoverall” score in the 1981 study includes an accuracy rate on the walk and turn test of just eight percent. Even the horizontal gaze nystagmus test, deemed most reliable in both studies, only identified 77 to 88 percent of impaired drivers accurately – a margin of error that could mean that as many as one in every four DUI arrests was based, at least in part, on inaccurate test results.

Field sobriety tests are notoriously difficult, even for sober drivers. If you’ve been charged with a DUI, the experienced New Hampshire DUI attorneys at Tenn And Tenn, P.A. can help. For a free and confidential consultation by phone, call us today at 1-603-624-3700.