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Experienced DWI Lawyers of Kurtz & Blum Discuss The Use Of Field Sobriety Tests In DWI Cases

Police Often Use "Standardized" Field Sobriety Tests, Or Roadside Tests, To Help Them Form An Opinion As To Whether Someone Is Impaired

If an officer stops you and suspects that you are driving while impaired, he or she may ask you to perform field sobriety tests.  Police officers use field sobriety tests, or FSTs, to find signs of impairment and to establish probable cause with which they can arrest you for DWI.  The National Highway Transportation and Safety Administration (NHTSA) has established three standardized sobriety tests, which are as follows:

  • Horizontal Gaze Nystagmus (HGN) Test
  • Walk-and-Turn Test
  • One-Leg Stand Test

Police officers may use other field sobriety tests to determine if someone is driving while impaired, but none of the other sobriety tests are scientifically validated to show impairment to any degree of certainty.  However, that doesn’t mean that the cop can’t testify about them or that a judge won’t consider them.  Despite a great deal of criticism that has been focused over the past few years on invalid forensic science, even the best criminal defense lawyer still can’t always stop this type of junk science from being admitted in court.

You have a right to refuse to take any field sobriety tests without consequence.  This is in stark contrast to the breath test.  In such situations, you may refuse to blow into a breath test thereby potentially limiting the officer’s power to observe you for signs of impairment, but you can still be arrested.  Once you are arrested, you cannot refuse a chemical test to measure blood alcohol content (BAC) without penalty.  Specifically, refusal to submit to a chemical analysis of your breath results in a one year revocation of your driver’s license.  Furthermore, once probable cause has been established, police can easily secure a warrant from a magistrate to draw your blood for chemical analysis.

DWI Roadside Tests Are Not Always ScientificIf you do consent to taking sobriety tests prior to being arrested for DWI, the officer will likely proceed with one or more of the standardized NHTSA field tests and may potentially administer other sobriety tests.  These tests are meant to test simple physical and mental capabilities in order to help determine if your BAC is above the legal limit.  The three standardized field sobriety tests must be administered systematically and require an officer to look for certain responses.  This does not mean that they necessarily administer them correctly.

Standardized Field Sobriety Tests

In the first standardized test, the Horizontal Gaze Nystagmus (HGN) test, the officer will have you track the movement of a pen or finger with your eyes.  Nystagmus is an involuntary jerking of the eye, which occurs naturally when you look to peripheral stimuli.  Scientific studies show that Nystagmus becomes more pronounced in the event of impairment.  Here, the officer is looking for six signs (three in each eye) that indicate impairment:

  1. Lack of smooth pursuit where eyes jerk as they focus on tracking movement
  2. Distinct and sustained nystagmus at maximum deviation (jerking where the eyes are stretched all the way to the side)
  3. Onset of nystagmus occurring prior to reaching a 45 degree angle

Four of the six potential signs indicate a BAC above the legal limit and can give rise to probable cause for the officer to arrest you for DWI.  However, even if you display four or more signs, there are a number of methods that can be used to attack the results and challenge the HGN test.  Certain medical conditions and legal substances, like caffeine or aspirin, can affect your performance on the test.  Additionally, the officer must be properly trained and administer the test with correct timing and movement else the test results will lack scientific validity.

As with the other field sobriety tests, the recent proliferation of video cameras in police cars has provided fertile material for both defense attorneys and prosecutors.  When police do the tests incorrectly, defense attorneys can effectively grill them with respect to their poor procedure and the accuracy of the results.  If they do everything correctly and impairment is clear on the video, it can prove extremely damaging to a defendant and difficult for even a highly skilled defense attorney to overcome.

The other two standardized field sobriety tests, the Walk-and-Turn test and the One Leg Stand test, are two-sided.  These sobriety tests require you to follow instructions while performing simple physical movements.

In the Walk-and-Turn FST, the officer instructs you to take nine heel-to-toe steps in a straight line.  The officer is supposed to provide you an actual line for guidance though many will ignore the standard procedure and ask you to walk an imaginary line.  Once nine steps have been taken, you will have to turn, per the officer’s instructions, and retake the steps back toward your original starting point.  The officer is looking for eight clues, only two of which are needed to indicate impairment and a BAC above the legal limit for purposes of DWI:

  1. Lack of balance while listening to the instructions
  2. Beginning before the instructions are finished
  3. Stopping while walking to regain balance
  4. Failing to touch heel-to-toe
  5. Stepping off the line
  6. Using arms to balance
  7. Making an improper turn
  8. Taking an incorrect number of steps.

In the One-Leg Stand field sobriety test, you must stand with one foot six inches off the ground while counting aloud until you are told to put your foot down.  An officer will look for four clues, two of which are needed to indicate a BAC above the legal limit:

  1. Swaying while balancing
  2. Using arms to balance
  3. Hopping to maintain balance
  4. Putting the foot down

If you take either of these two tests and perform poorly, there are still ways to attack the results.  Officers must administer the tests correctly and be properly trained. Medical conditions can affect your ability to walk or balance.  Weather, location, surroundings, your weight, and even your choice of clothing can also factor into a poor performance. 

Other Sobriety Tests

Once you have completed these standardized tests, the officer may proceed with other field sobriety tests or arrest you if he or she feels there is adequate probable cause for DWI.  Other tests are not NHTSA approved and have not been scientifically validated, but that doesn’t stop police and courts from using them.

Portable Breath Tests Can Be UnreliableIf the officer administers other sobriety tests, he or she will often ask you to take a portable breath test, or PBT.  A PBT may not be used to prove guilt of impaired driving in court.  It may only be used, along with other field sobriety tests, to prove that there was probable cause for arrest.  If you elect to take a portable breath test, the officer will have you blow twice into the instrument with the second blow occurring a few minutes after the first.

There are ample opportunities for attacking the results from a PBT.  The instrument must be properly documented, maintained, and calibrated. Like the other field sobriety tests, the officer must be properly trained and follow definitive guidelines.

Other field sobriety tests that an officer may administer outside of the three standardized tests discussed above and the portable breath test include:

  • The Romberg balance test, which requires you to hold your balance for approximately 30 seconds when standing with your feet together, head back, and eyes close.
  • Finger-to-nose test
  • Reciting parts of the alphabet
  • Finger counting by touching thumb to fingers also known as the “Finger Dexterity Test”
  • Counting backwards

Law enforcement touts field sobriety tests as reliable at indicating impairment and a blood alcohol content above the legal limit.  However, even the three standardized tests can result in errors.  Officers must be trained properly and follow strict guidelines.  If you perform poorly, your results can be fought and potentially suppressed.  If suppressed, it can be exceedingly difficult for a prosecutor to establish that the law enforcement officer had probable cause to arrest you and everything that comes after arrest will be suppressed as well.  If the arrest is suppressed, no evidence will remain from which a court can convict you of DWI.

Our DWI lawyers help people throughout Wake County, North Carolina.  We frequently handle offenses arising out of the following cities: New Hope, Cary, Morrisville, Rolesville, Zebulon, Apex, Knightdale, Wendell, Fuquay-Varina, Holly Springs, Wake Forest, Garner and Raleigh.