In order to identify citizens who are driving under the influence of alcohol and certain drugs, police will often use Field Sobriety Tests to determine if a driver is under the influence. A driver is said to be under the influence of alcohol if their blood alcohol concentration is above 0.08%, and in commercial drivers the limit is set at 0.04%.
If a police officer believes that a driver is intoxicated, they may ask the driver to submit to several field sobriety tests. The horizontal gaze nystagmus test, the walk and turn test, and the one leg stand test are 3 field sobriety tests that are often used.
The horizontal gaze nystagmus test can identify the use of alcohol or other drugs that depress the central nervous system by showing a nystagmus in the eye. A nystagmus is involuntary bouncing or jerking of the eyeball that occurs when one looks to the side. This involuntary bouncing or jerking can be either caused by alcohol intoxication or the use of other drugs such as inhalants or phencyclidine (aka PCP or Angel Dust). Alcohol and certain other drugs depress the central nervous system making it difficult for the brain to control the eye muscles. To administer the horizontal gaze nystagmus test, a police officer will position an object such as a pen or a finger about a foot away from the driver’s view. The officer will then note any bouncing or jerking movements of the driver’s eyes as they follow the pen with their eyes from side to side.
The walk and turn test is another method that aids officers in determining whether or not a driver is under the influence. During this test, the officer gives the driver simple instructions to follow: walk in a straight line keeping their arms at their side, putting one foot in front of the other with the heel of one foot touching the toes of the other. The officer will instruct the driver to take nine steps forward while counting the steps, and turn around at the 9th step and return to the starting point by taking 9 more heel-to-toe steps. If the officer observes that the driver stops or starts the field test before instructed to do so, has trouble balancing during the test, uses their arms to balance while walking, fails to step heel-to-toe, steps off of the line, or uses an improper number of steps, the officer may conclude that the driver is under the influence.
During the one leg stand test, an officer will demonstrate and explain what is expected of the driver. The officer will show the driver the correct standing position; standing with feet together and arms at the sides, and then raising either leg up six inches off the ground, and counting up from 1000 all the way up to 1030. If a driver raises their arms more than 6 inches up from their sides to keep balance, rests the elevated foot on the ground more than 3 times during the 30 seconds, hops to keep their balance, or sways during the test, the officer may conclude that the driver is intoxicated.
Although these tests can help in determining whether or not a driver is under the influence, the tests are by no means perfect 100% of the time. For example, the elderly, people with back, neck, or leg issues or people who are overweight may have trouble with the one leg stand and walk and turn tests even when sober. These tests are usually followed by the horizontal gaze nystagmus test or a breathalyzer test to ensure accuracy.
If you or a loved one has been charged with drunk driving (OUI, DWI, DIU) please contact us for a consultation.