Only three DWI Field Sobriety Tests are recommended by National Highway Traffic Safety Administration (NHSTA), and of those three, they are -- at best -- 77% accurate, according to the latest studies by National Highway Traffic Safety Administration (NHSTA). Still, the tests are routinely given and are often inaccurate instruments of intoxication.
On this DWI FST, an officer will ask a DWI suspect to walk in a straight line, sometimes on a painted line if available, for about nine steps, and then turn and walk nine steps back. The steps are to be heel to toe, each way, and if any gap is noticed, the officer will use the observation as a sign of intoxication. Likewise, if any stumbling or hesitation occurs, that will be noted as a DWI symptom. To make matters worse, if the DWI suspect attempts to walk too quickly, the police report may note the suspect was too eager and moved to quickly. Again failing the test.
The DWI Field Sobriety test known as the Line Walk is rarely used, although many police officers ask for the test since it is easy to report mistakes, thereby reinforcing the officer's belief of DWI. Typically a shoulder road line is used, if safe, where the DWI subject is asked to walk the line as straight as possible.
On this test, a person suspected of a Austin Texas DWI is asked to stand straight, with both arms stretched out to either side, and then bend one arm at the elbow to touch the tip of their pointer finger to the tip of the nose.
Standing on one leg, a DWI suspect is asked to hold the position without hopping about or falling. This test is difficult for most people who have not had any alcohol.
An officer will tell a DWI suspect to count in their head to thirty, letting the officer know when the count is finished. On a stopwatch, the officer records the actual passage of time, in an effort to show the delay in brain processing (often very intoxicated people may count to 45 or longer when the thirty seconds are up).
Common years ago, this test has almost zero correlation to determining intoxication since less than half the population fails at spelling the alphabet backwards when sober.
This DWI test is where officers move either a finger or a small pen or flashlight in front of a person's eyes to judge the pupil and iris slightly bouncing, caused by alcohol consumption. Horizontal Gaze Nystagmus cannot be used to determine BAC levels, however it may detect whether there is alcohol in the body.