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Walk the Line

Field sobriety tests in Pennsylvania

We have all seen comic film versions of a drunk driver unable to touch his nose, or stagger happily down the road under the watchful gaze of law enforcement.  But it is not funny.

Standardized Field Sobriety Tests (SFST) were developed by the Southern California Research Institute for the National Highway Traffic Safety Administration (NHTSA).  Field sobriety tests are used across the country by law enforcement to detect and detail the behavior of impaired drivers.

With proper administration of field sobriety tests, NHTSA reports the combined accuracy of the tests is 91 percent for detecting a blood alcohol concentration (BAC) of .08 percent.  The three standard tests are:

  • One Leg Stand (OLS)
  • Walk and Turn (WAT)
  • Horizontal Gaze Nystagmus (HGN)

Under Pennsylvania law, drivers are required to submit to a blood alcohol test but not field sobriety tests—and that may be smart due to concerns about their accuracy.  SFST are routinely used as support for probable cause for arrest.

A 1998 study found these three standardized tests have accuracy rates between 79 and 88 percent.  Designed to evaluate both psychological and physical impairment, results can be skewed by legal medication, physical injury or inability, the normal aging process, or simple inattention to detail during the stress of a roadside stop.

Our firm has fought drunk driving charges for our clients for decades.  Challenging probable cause for arrest is an essential defense if you choose to walk the line.

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