When a police officer pulls someone over under the suspicion of DWI, they may ask the driver to step out of the car and perform several tasks—known as field sobriety tests (FSTs)—to determine their level of intoxication. The three most common field sobriety tests drivers are asked to perform are the one-leg stand, the walk-and-turn, and the horizontal gaze test.
Since police departments use FSTs to determine probable cause in DUI arrests, many believe that these tests are accurate. However, there are some studies that show how inaccurate and ineffective these tests can be.
The History & Accuracy of Field Sobriety Tests
The NHTSA gave an assignment to the Southern California Research Institute (SCRI) in the late 1970s, tasking them to assess several field sobriety tests used in the field in order to determine their accuracy. The SCRI brought in ten officers to evaluate subjects and determine if they had a BAC of .10% or greater.
Once the subjects have been scrutinized, the institute suggested that the walk-and-turn, the one-leg stand, and the horizontal gaze nystagmus are reliable enough to evaluate intoxication. However, there was a 47 percent error rate by the officers.
The NHTSA decided that the institute conduct these tests again in 1981 in an effort to reduce the error rate. Again, the results were not great. The horizontal gaze these could correctly identify someone with a BAC over .10 only 77 percent of the time. The one-leg stand test was correct 65 percent of the time. The walk-and-turn test was accurate 68 percent of the time. When all three were used together, they were right 82 percent of the time.
Should You Take a Field Sobriety Test?
The short answer is no. Field sobriety tests are not a requirement in Texas.
You can politely decline to take an FST. Remember, taking the tests can only give an officer more probable cause to arrest you.