If you've ever made the poor choice to drive drunk and gotten pulled over, most likely the officer who stopped you performed a battery of field sobriety tests aimed at confirming their suspicions. The most popular of these, roadside sobriety and Breathalyzer tests, are used to enforce DUI laws.
As for field sobriety tests, there are two different versions -- a standardized one and a non-standardized one. While the former is endorsed by the National Highway Traffic Safety Administration, the latter is not.
When it comes to the standardized field sobriety test, it involves the performance of three competency exercises. These include the horizontal gaze nystagmus, the walk-and-turn, and the one-leg stand.
The HGN test measures the jerking of a driver's eye that is more pronounced than it otherwise would be under normal circumstances. As for WAT test, the inability of a suspect to take nine steps, by placing one foot in front of the other and to repeat it is equally suggestive of the same.
The OLS test requires those suspected of driving drunk to stand on one leg with the other lifted at least six inches in the air. Any instance in which one exhibits difficulties balancing, hops, or can't keep their leg raised for a 30-second duration has the potential of being cited as failing that particular test.
The aggregate results of these three tests, if effectively performed, have been proven to be capable of accurately pinpointing alcohol impairment in up to 91 percent of all cases. They've been shown to be 94 percent effective in cases in which explanations are given for false positives.
Even given the relatively high accuracy rates of field sobriety tests, a Breathalyzer test is generally performed to verify the suspect's blood alcohol level.
If you or someone you know has been arrested on suspicion of driving drunk, a North Carolina DUI attorney can provide advice and guidance.
Source: FindLaw, "Field Sobriety Tests," accessed Feb. 17, 2017