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Standard field sobriety tests may not always be accurate

When a person imagines what it would be like to be pulled over by a police officer on suspicion of drunk driving, he or she might include field sobriety tests in the mental picture. These tests are supposed to help cops detect signs of intoxication, so it might be natural to wonder: Are they actually effective?

According to the National Highway Traffic Safety Administration, a set of three field exercises (known collectively as the Standardized Field Sobriety Test) were developed to pick up on clues of intoxication and impairment. Although the tests are typically the same, interpreting the results can be a subjective process.

To better understand the effectiveness of the field sobriety tests, it may be helpful to take a look at the three standard examinations:

  • Horizontal Gaze Nystagmus: In this test officers will ask a suspected individual to follow an object moving from side to side. Officers look for involuntary jerking motion in the eyes, which can be a sign of intoxication. However, this can also be a natural side effect of certain prescription drugs. The NHSTSA says this test is 88 percent accurate.
  • Walk-and-Turn: Although the substance of the test is pretty self-explanatory, the purpose is to test attention division. People might not be able to complete actions and follow instructions when they are impaired by drugs or alcohol. Research from the federal agency shows that this test is effective 79 percent of the time when officers follow specific guidelines.
  • One-Leg Stand: Standing on one foot while counting aloud tests balance and, once again, an individual's ability to divide attention. When police identify certain markers, the NHTSA says this test is 83 percent accurate.

Although police officers are typically trained how to administer and interpret the standard field sobriety tests, they are not a sure-fire indicator of impairment.

If a people are pulled over at a late hour, with bright lights shining on them, it's not shocking to think that nerves could take over and produce a false positive. Not only that, but pre-existing physical limitations could make it impossible to pass these tests, even without having consumed any alcohol.

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