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Standardized Field Sobriety Tests in North Carolina DWI Arrests

In 1981 and again in 1998, the National Highway Traffic Safety Administration (NHTSA) along with the Southern California Research Institute put together a battery of roadside tests to help law enforcement determine if a motor vehicle driver was impaired. They came up with three tests: the Horizontal Gaze Nystagmus test (HGN); the Walk and Turn test (WAT); and the One Leg Stand test (OLS). NHTSA developed these tests to be administered in a standardized manner to obtain indicators of impairment and establish probable cause for arrest. Each of these tests has a series of clues that the officer looks for when administering the tests. From the 1998 study, officers used these tests to establish an arrest at a .08 BAC standard. The results were as follows: if the officer observed four or more clues of the HGN in the driver, 88% of the time the driver was a .08 BAC or higher; If the officer observed two or more clues on the WAT in the driver, 79% of the time the driver was a .08 BAC or higher; and on the OLS if the officer observed two or more clues in the driver there was a 83% of the time the driver was a .08 BAC or higher. All three tests combined showed a 91% accuracy rate in finding impaired drivers.

The Horizontal Gaze Nystagmus Test or HGN in North Carolina DWI Arrests

In the Horizontal Gaze Nystagmus test or HGN, the officer is looking for a total of six clues, or three in each eye. First the officer checks for equal size and tracking, and then he checks for lack of smooth pursuit, distinct nystagmus at maximum deviation, and onset of nystagmus prior to 45 degrees. Here’s how the test is supposed to be done:

  • Remove eyeglasses
  • Check pupils for equal size
  • Check eyes to insure they both track stimulus equally
  • Begin with the left eye
  • Check each eye independently
  • Hold stimulus 12-15 inches in front of nose
  • Check for a lack of smooth pursuit (center to side in 2 seconds)
  • Check both eyes twice to confirm observations
  • Check for distinct nystagmus at maximum deviation (hold at maximum deviation for a minimum of 4 seconds each time, nystagmus must be distinct and sustained)
  • Check both eyes twice to confirm observations

The Vertical Gaze Nystagmus test or VGN is part of the HGN test and is done last. For what it’s worth, NHTSA has said “Vertical nystagmus was not examined in the original research that led to the validation of the SFST battery” The Vertical Gaze Nystagmus is supposed to be given in this fashion:

  • Position stimulus 12-15 inches from nose
  • Raise stimulus until the subject’s eyes are elevated as far as possible
  • Hold for approximately 4 seconds

The Walk and Turn Test or WAT in North Carolina DWI Arrests

The Walk and Turn test or WAT is as it implies, a walking test. The officer is looking for a total of 8 clues in this test:

  1. Can’t balance during instructions
  2. Starts too soon
  3. Stops
  4. Misses heel to toe by 1/2 inch or more
  5. Steps off the line
  6. Uses arms for balance
  7. Turns incorrectly
  8. Wrong number of steps

Even though NHTSA has said these tests are not pass/fail tests, if the officer observes two or more clues on the WAT the officer will conclude that you did not perform the test to his or her satisfaction. Here’s how this test should be given:

  • Instruction stage: left foot on line, right foot directly in front of left foot with heel touching toe
  • Do not move from this position until told to do so
  • Do you understand?
  • Walking stage-when told to begin, take nine steps heel touching toe, when you reach your ninth step, leave your lead foot on the line and turn making a series of small steps, and then return nine steps heel to toe. While you are doing this, keep your hands at your side, watch your feet at all times, count out loud, and don’t stop until you’ve completed the test.
  • Do you understand these directions?

NHTSA has said “The original research indicated that individuals over 65 years of age, back, leg or inner ear problems had difficulty performing this test. Individuals wearing heels more than two inches high should be given the opportunity to remove their shoes.”

The One Leg Stand Test or OLS in North Carolina DWI Arrests

The One Leg Stand test or OLS is a timed test. The officer is looking for a total of four clues:

  1. Sway
  2. Arms to balance
  3. Hops
  4. Puts foot down

Once again, if the officer observes two or more clues in this test you will not have completed it to his or her satisfaction. Here’s how the test is given:

  • Instruction Stage-stand with feet together and arms at side, don’t move from this position until told to do so.
  • Do you understand?
  • Raise either foot of your choice approximately six inches off the ground keeping foot pointed
  • Keep both legs straight
  • Look at your elevated foot
  • Count out loud: one thousand one, one thousand two, and so on until told to stop
  • Officer must time for 30 seconds

Winston-Salem DWI Attorney J. Scott Smith

You need an attorney that understands this battery of standardized tests. Mr. Smith has successfully completed the NHTSA Standardized Field Sobriety Tests 24 hour course. This is the same training that is given to the police officer. Call our office for your free DWI consultation today.