Standard Field Sobriety Tests (SFSTs) do not accurately determine impairment for probable cause to support an arrest for Driving Under the Influence (DUI).
The SFSTs originally researched by the National Highway Traffic Safety Administration (NHTSA) fail to provide a standardized means of objectivity and unscientifically assessing impairment. The SFSTs were originally developed to assist the officer screen a driver for probable cause to arrest the indivudual for drunk driving. Yet frequently the officer gives the SFSTs after deciding that the driver is guilty of DUI.
The effectiveness of the SFSTs has been called into question since they were developed by NHTSA and are therefore "self-serving". In a 1977 study, researchers learned that 47 percent of the subjects that would have been arrested based upon test performance actually had blood-alcohol concentrations less than the legal limit of 0.10 (the legal limit was reduced to 0.08 in 2000). In 1981, the same researchers conducted further "standardized" testing and learned that the the false results dropped to 32 percent: in other words, in this test nearly one out of every three individuals who failed the test were not legally intoxicated.
Subsequent independent scientific researchers have found these Standard Field Sobriety Tests flawed. Many of these same researchers in 1987 observed that the SFSTs determined balance, steadiness, and reaction time but concluded that a connection between these factors and driving ability was not apparent because neither a steady stance nor simple movement time is essential to the safe operation of a motor vehicle. The researchers did concede that the Standard Field Sobriety Tests may show the presence of alcohol, but that they did not necessarily measure driving ability.
Research on the validity and accuracy of the Standard Field Sobriety Tests conducted in 1991 at Clemston University further showed the SFST's yield false results. In this study, 21 sober individuals with a blood alcohol content of .00 were videotaped performing six common Field Sobriety Tests. The videotapes were then shown to 14 officers who were asked to determine if the individuals had too much to drink and drive. The officers were not informed that the individuals on the videotapes were sober. The officers found that 46 percent of the time the individuals were too intoxicated to drive.
Generally officers do not give the Standard Field Sobriety Tests uniformly, and as noted, there is no scientific basis for assuming they are valid. Many officers either administer the wrong tests or improperly instruct the suspect driver on how to perform the tests. A DUI defense attorney can obtain a pretrial suppression ruling to exclude the SFSTs and their alleged indication of impairment due to lack of scientific foundation and improper instructions.