Field Sobriety Test – Officers commonly use the same three tests. These tests are not mandatory and can be refused, although officers will never inform you of this.
Horizontal Gaze Nystagmus Test or HGN is a test where the officer requests the individual follow a pen or their finger. The officer is looking for nystagmus or an involuntary jerking or bouncing of the eyeball that occurs. Horizontal gaze nystagmus (HGN) refers to a lateral or horizontal jerking when the eye gazes to the side. An officer is looking to see if the eyeball tracks left to right smoothly, if nystagmus occurs at a 45 degree angle and if nystagmus is present at maximum deviation, or your peripheral vision. In the impaired driving context, alcohol consumption or consumption of certain other central nervous system depressants like inhalants or phencyclidine, hinder the brain’s ability to control eye muscles, therefore causing the jerk or bounce associated with HGN. As the degree of impairment becomes greater, the jerking or bouncing becomes more pronounced.
The 9 step walk and turn test is the second common test. For this test, an officer will have an individual stand with their hands at their side and one foot in front of the other standing heel-to-toe. While standing in this fashion, the officer will demonstrate walking 9 steps heel-to-toe on an imaginary line. After step 9 a turn will be made by making a series of small steps before making 9 steps back to where you originally started. The officer is not only concerned about how an individual performs on the test, but also how they listened to the directions.
The one leg stand consists of an individual standing on one leg with their arms at their side (up to 6 inches from body) counting to 30. The officer will provide directions prior to the individual starting the test. Again, the test is not only of the physical performance, but also how well directions are followed.
If the tests are preformed as trained in, a controlled setting they are up to 90% accurate in detecting an individual is intoxicated. Officers cannot perform the tests correctly 100% of the time as done in various studies. Furthermore, the tests performed by the officer are in the field not a classroom. Weather, area where the tests are completed, and individual’s own medical and physical conditions all lead to the test being subject to harsh criticism.
Upon completion of the standardized field sobriety tests, the officer will request a PBT. The officer does not have to show you the results of the PBT.