How accurate are field sobriety tests?

You’ve probably driven past someone who has been pulled over by police and subjected to a series of field sobriety tests. From afar, the process may look very scientific, with the officer observing the driver’s movements very methodically to try and determine if he or she may be impaired.

Yet if you have ever participated in such an exercise yourself, you may view the conclusions made by the officer as little more than estimates. In today’s post, we’ll discuss these field sobriety tests in a bit more detail, including controversy over how accurate they supposedly are.

The National Highway Traffic Safety Administration has created a series of Standardized Field Sobriety Tests for officers to use in attempting to determine if a suspect may be intoxicated. These include:

  • An observation of a suspect’s horizontal gaze (called the horizontal gaze nystagmus test)
  • A standard “walk-and-turn” test along a straight line
  • A one-legged stand test
  • A recitation test

The NHTSA backs up its SFSTs with statistics showing that they are accurate in determining if a suspect is impaired in 91 to 95 percent of cases. Yet when put to the test by other researchers, a number of flaws with the methods of following SFSTs were identified.

Research done by shows that of the sample of drivers studied, almost 20 percent who had blood-alcohol concentration levels below the legal limit actually failed the tests. Further analysis showed that of the cases where the tests indicated that the driver was not impaired, those results were ignored 59 percent of the time.

Field sobriety tests can be skewed by a number of factors, including the overall health and coordination of the person being tested. A young, athletic man might be able to confidently stand on one leg even though he is very intoxicated, while an older man with bad knees might fall over even with no alcohol in his system.

So much of determining impairment and intoxication in a field sobriety test is subjective. An experienced attorney can examine every aspect of the traffic stop that led to your arrest – including the field sobriety tests – to determine if errors were made.

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