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Field Sobriety Tests

police car

In this blog, we will provide a brief overview of the common field sobriety tests performed on individuals suspected of DUI.

The National Highway Traffic Safety Administration (NHTSA) includes the Horizontal Gaze Nystagmus, the Walk and Turn, and the One Leg Stand as the three standard field sobriety tests to determine whether a driver is under the influence.

Horizontal Gaze Nystagmus (HGN) 

This is where the police officer places the tip of his finger, a pen, or some other object in front of a driver’s face, moves the object back and forth, and observes the driver’s eye movements. During the test, the officer looks for 1) lack of smooth pursuit – whether the eye is jerking as it moves, 2) whether nystagmus sets in before the eye reaches a 45 degree angle, and 3) distinct and sustained nystagmus at maximum deviation – eye jerks for a minimum of four seconds while looking all the way to one side. While the HGN is generally accepted and widely used in assessing a person’s BAC, there are many ways to challenge the test.

Walk and Turn

 An officer will first explain and demonstrate the walk and turn test to a driver. The driver will place his or her foot in front of the other, touching heel to toe, and walk on a straight line for nine steps. The driver will then turn around, taking a series of small steps, and walk back on the same straight line by taking another nine heel-to-toe steps. Officers will look for whether the driver:

  • Fails to maintain balance
  • Starts too soon
  • Stops while walking
  • Steps off the line
  • Improper turn
  • Misses heel-to-toe
  • Raises arms for balance
  • Incorrect number of steps

One Leg Stand

 A driver is instructed to stand with their arms down by their side and with one foot approximately six inches off the ground and to count aloud (one thousand one, one thousand two, etc.) until instructed to stop. This should be performed on a level, non-slippery surface. Officers look for swaying, hopping, using arms for balance, and putting foot down.

Modified Romberg Test

 This non-standard field sobriety test that is most often used to detect whether an individual is under the influence of drugs or a controlled substance. A driver stands with his or her feet together, closes their eyes, tilts their head back, and estimates the passage of 30 seconds. The test makes a driver divide his or her attention to multiple mental and physical tasks simultaneously.

Preliminary Breath Test (PBT) 

Likely the last field sobriety test given, the PBT is a small device that a driver blows into for the purpose of checking their BAC level. A PBT can only be administered if a law enforcement officer has reason to believe a person has committed a DUI offense. An office must observe a driver for 15 minutes prior to this test to ensure that he or she did not smoke, eat, or drink anything during that time period. The results of a PBT are not admissible in Court but only serve to guide the officer in deciding whether an arrest should be made.