While we tend to have many ideas of what a field sobriety test might look like thanks to TV and movies, there is a standardized test from the National Highway Traffic Safety Administration. If a person is driving erratically, a police officer might pull them over to make sure they aren’t driving drunk. Then, they might administer the Standard Field Sobriety Test which consists of three tasks. These measure balance, coordination, and the ability to concentrate on two things at once. This battery of tests includes the horizontal gaze nystagmus, the walk and turn test, and the one-leg standing test. If a driver fails any of these, the cop will likely use a breathalyzer to determine their blood alcohol level.
The Standard Field Sobriety Test for Drunk Driving
Horizontal Gaze Nystagmus
The first part of the Standard Field Sobriety Test is the horizontal gaze nystagmus. To do this test, an officer has a person follow an object with their eyes from side to side. When we follow an object with our gaze, our eyeballs involuntarily ”jerk” as our eyeballs look more to the sides. A person who is under the influence, their eyes jerk more often than a sober person. In addition, they might have trouble concentrating on the object. If the person fails this test, it’s around 77% likely that their blood alcohol content is above 0.10.
Walk and Turn Test
Another classic movie example that is part of the Standard Field Sobriety Test is the walk and turn test. An officer will ask somebody to walk a straight line going heel to toe for nine steps, then turn around and walk nine steps heel to toe back. They look to see if the person can follow directions and maintain their balance. A person who fails several aspects of this test is 68% likely to have a blood-alcohol level above 0.10.
One Leg Standing Test
Finally, the last step of the Standard Field Sobriety Test is the one-leg standing test. In this, a person must stand with one foot about six inches above the ground and count up from 1,001 for about thirty seconds. The officer is watching their ability to follow directions and balance. If they fail aspects of this test, they’re 65% likely to have a blood-alcohol level above 0.10.
Failure
When an officer gives a driver the Standard Field Sobriety Test, they are looking to compare results across all three steps. None of these are 100% accurate. Therefore, comparing results across all three can give them a better sense of whether or not a person is under the influence. If they do fail some of these, they’ll be given a breathalyzer test or blood analysis to determine their actual BAC level. If they are driving under the influence, they can face serious penalties. For example, a DWI ticket, jail time, fines, points on their license, or even losing their license.
Driving under the influence is a serious problem, so officers are always on the lookout for drivers that seem to be impaired. If they do pull somebody over, they’ll speak to them and determine if a field test is needed. When they do field testing, they follow the Standard Field Sobriety Test. This consists of the horizontal gaze nystagmus to test for eye movement. In addition, they’ll also perform the walk and turn test and one leg standing test to check for balance, coordination, and ability to follow directions. If a person fails any of these tests, the officer will use a breathalyzer or blood test. This way, they can determine the person’s blood alcohol content. Now that cabs and ride-sharing services are easily available, there is never a reason to get behind the wheel of a car after drinking.