Standard field sobriety tests do not accurately measure driver impairment

 By Stephen J. Isaacs, JD
© The Medical-Legal News 2007

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, thus unscientifically assessing impairment. The SFSTs were originally developed to assist the officer to screen a driver for probable cause to arrest the individual 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 on test performance actually had blood-alcohol concentrations less than the legal limit. In 1981, the same researchers conducted further “standardized” testing and learned that the false results dropped to 32 percent. In other words, in this test nearly one out of every three individuals who failed the test was not legally intoxicated.

Subsequent independent scientific researchers have found the SFSTs flawed as well. 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 SFSTs 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 Clemson University further showed that the SFSTs yield false results. Videotapes were shown to 14 officers who were asked to determine if the individuals in the tapes had too much to drink. The officers were not informed that the individuals on the videotapes were sober. The officers opined that 46 percent of the individuals were intoxicated.

Generally, officers do not give the SFSTs uniformly, so 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. An attorney can obtain a pretrial suppression ruling to exclude the SFSTs and their alleged indication of impairment due to lack of scientific foundation. •

Stephen J. Isaacs of the Isaacs Law Office is a member of The M-L News editorial board; isaacs@legal-lifeline.net.