During a Driving While Impaired (DWI) stop in North Carolina, the officer typically makes the suspect perform any number of field sobriety tests in order to determine whether the suspect is intoxicated. The National Highway Traffic Safety Administration (NHTSA) has developed a battery of three standardized field sobriety tests, which are used by federal, state, and local law enforcement officers in North Carolina for determining whether a DWI arrest is appropriate. These standardized field sobriety tests are: the Horizontal Gaze Nystagmus test, the Walk-and-Turn test, and the One-Leg Stand test.
Horizontal Gaze Nystagmus Standardized Field Sobriety Test
When done properly, the Horizontal Gaze Nystagmus test is the single most reliable test of the standardized field sobriety tests at an officer’s disposal. In this test, the officer has the suspect follow an object on a horizontal (side to side) plane with their eyes. While doing this, the officer looks for evidence of nystagmus of the eyes. Nystagmus is the involuntary jerking of the eyes, which can be caused by any number of things, including alcohol or certain drug use. In conducting this test, the officer is looking for six total clues (three for each eye) which would indicate impairment:
- The lack of smooth pursuit of the object by the eye;
- Distinct and sustained nystagmus at maximum deviation (when the eye is held by fixation on the object at the furtherest angle the eye can see the object); and
- Onset of nystagmus of the eye prior to a 45 degree angle.
Typically, as a person’s blood alcohol concentration increases, it is more likely that these clues will appear. NHTSA has trained officers that if four or more clues are exhibited by a person’s eyes during this standardized field sobriety test, it is likely that the driver’s blood alcohol concentration is above 0.10.
Walk-and-Turn Standardized Field Sobriety Test
The Walk-and-Turn test is a standardized field sobriety test aimed at dividing a driver’s attention, as it requires a driver to multi-task. In this standardized field sobriety test, the officer should begin by instructing the driver what he wants the driver to do and then offer a brief demonstration of how to perform the Walk-and-Turn. During the test, the driver will walk nine steps in a heel-to-toe manner with their hands by their side, turn, and repeat the nine steps back to the officer. While the suspect is performing this test, the officer will be observing the test and looking for the following clues:
- Driver cannot keep balance while listening to instructions;
- Driver starts performing the test before the instructions are finished;
- Driver stops for several seconds while walking (walking slowly does not satisfy this clue);
- Driver does not touch heel-to-toe (must be more than a 1/2 inch gap between heel and toe);
- Driver steps off the real or imaginary line;
- Driver uses arms to balance;
- Improper turn by the driver; and
- Incorrect number of steps by the driver.
NHTSA has trained officers that if two or more clues are evidenced by the driver during this standardized field sobriety test, or if the driver cannot complete the test, the driver’s BAC is is likely to be above 0.10.
One-Leg Stand Standardized Field Sobriety Test
The One-Leg Stand test is another divided attention test. In this test, the officer first instructs the suspect on how the test will be conducted, then has the driver perform the test. In the test, the driver will stand with their feet together with their arms at their sides, lift one foot six inches off the ground, and hold it there while counting out loud until told to stop by the officer. While the driver is performing the test, the officer will be looking for the following clues:
- Driver sways while balancing;
- Driver uses arm for balance;
- Driver hops to maintain balance; and
- Driver puts his/her foot down.
NHTSA has trained officers that if two or more clues are evidenced during this standardized field sobriety test, the driver’s BAC is is likely to be above 0.10.
Standardized field sobriety tests are only accurate to the extent that they are conducted in a systematically correct way by the officer. Problems occur when:
- An officer gives inadequate instructions or demonstrations to the driver;
- An officer incorrectly performs the test (particularly during the HGN standardized field sobriety test);
- An officer conducts the test in inadequate conditions, lighting or terrain (not discussed above); or
- An officer fails to ask the necessary pre-qualifying questions to make sure the driver is an appropriate candidate for performing the test (not discussed above).
If you have been charged with DWI, call our office now to discuss the details of your case and explore defense you can raise at trial.