The (In)Accuracy of Field Sobriety Tests

Field sobriety tests are commonly used by police officers to evaluate the condition of individuals they believe to be driving while intoxicated. Three tests have been approved by the National Highway Traffic Safety Administration as scientifically valid. Unfortunately, these tests are far less accurate than their prevalence would lead one to assume. Below are these three standardized field sobriety tests and their accuracies (expressed in percentages):

HGN – The Horizontal Gaze Nystagmus, which uses a driver’s eye movement to detect potential impairment, is 77% accurate.

Walk and Turn – This divided attention test requires the driver to walk nine steps heel-to-toe in a straight line, then turn and take nine heel-to-toe steps back across the same line. It is only 68% accurate.

One Leg Stand – In the one leg stand, the driver is instructed to stand with one leg 6 inches off the ground for 30 seconds. This test is just 65% accurate.

Often, a sober person may fail to perform these tasks under normal circumstances. Add the nervousness that getting stopped by law enforcement inevitably provokes, and the ability to pass these tests becomes a far more difficult feat. Furthermore, this set of assessments has not even been validated for those with medical conditions, people 65 years or older, or individuals 50 pounds or more overweight.

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If you have been accused of DWI, you should do everything possible to fight the harsh consequences that may accompany a conviction. For the experienced legal assistance you need, contact a Dallas DWI attorney at the Law Offices of Mark T. Lassiter today at (214) 845-7007.


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