Are Field Sobriety Tests Reliable In DWI Arrests? Several Studies Question FST Reliability

Guest Author: Allison Gamble, Student of Psychology

Arrests and convictions for charges of driving under the influence are often made based on evidence from field sobriety tests. While law enforcement officers often contend these tests are foolproof, forensic psychology and the statistics show otherwise. In a substantial number of cases field sobriety tests tend to indicate individuals are intoxicated when their blood alcohol levels are still below legal limits. A revision of the way this testing is performed may be necessary to prevent wrongful DUI charges.

There are several types of field sobriety tests used, and none has proven infallible in peer-reviewed research. On the contrary, studies often reveal significant problems with these tests. The horizontal gaze nystagmus (HGN) test looks for involuntary eye movements as an individual is told to look at a certain point in space. Even the US Department of Transportation states this test only accurately detects intoxicated people 88 percent of the time. A separate study performed by Maryland law enforcement officers found it was only accurate 79 percent of the time, and about one third of subjects below the legal blood alcohol limit were wrongly identified as intoxicated using this test.

Another common way to detect drunk drivers is with the walk and turn test, or a test involving standing on one foot. The Department of Transportation states these tests are about 79 percent and 83 percent accurate, respectively. However, critics of these methods point out the studies from which these statistics are derived were conducted by highly motivated officers specially trained to administer these tests, and who were being observed by civilian analysts. They point out that in actual roadside situations the detection rate could be much higher, and officers may be simply looking to make arrests, and so will tend to interpret cues in such a way that they will believe people are intoxicated, even if they legally aren’t.

Some peer-reviewed studies have been even more critical of these tests. They state these tests are only accurate around two thirds of the time in detecting inebriated individuals, and often lead to false positives in assessing sober subjects. These studies found that only rarely were people who hadn’t had anything to drink actually judged to be completely sober, even if officers didn’t deem them “too drunk to drive.”

Even field sobriety tests using breathalyzers aren’t always accurate. The Department of Transportation has stated these devices accurately detect blood alcohol content about 91 percent of the time. Accordingly, all else being equal breathalyzer detections will be incorrect almost one time in ten. Moreover, depending on the skill of officers in administering other field sobriety tests and properly gauging subjects’ responses, individuals could still easily be wrongly arrested for DUIs. When the only completely reliable determination of blood alcohol content is a blood test, being exonerated after the fact is impossible.

The tests currently used to evaluate sobriety in the field have unacceptably high false positive rates, and don’t always detect intoxicated individuals consistently enough to be considered reliable. Often officers’ own motivations, experiences, and beliefs regarding the people they’re testing will lead to arrests more than testing does. Until more accurate field tests of blood alcohol levels are available, the results of these tests should always be supplemented by actual blood testing in order to absolutely prove someone has been drinking and driving.

St. Louis Missouri DWI Lawyer, Gary Lauber, is an expert in defensing drunk driving cases and successfully asserting defenses based on the lack of evidence established by the Filed Sobriety Tests and other circumstances surrounding the DUI arrest. Contact DWI Defense Lawyer Today.