Being asked to step out the vehicle and perform field sobriety tests is nerve-wracking for any driver, even those not under the influence. Knowing a little bit more about what you are asked to do and what the officers are looking for can help ease that anxiety.
What are Field Sobriety Tests?
Field Sobriety Tests are tests administered by police officers during a traffic stop to determine if a driver is under the influence of alcohol and/or drugs. These tests are standardized across the United States, and police officers are trained with materials from the National Highway Traffic Safety Administration.
There are 3 Standardized Field Sobriety Tests in Illinois. Let’s look at each one individually.
Horizontal Gaze Nystagmus (HGN) – involuntary jerking of eyes as the eyes gaze to the side
What you are asked to do: use your eyes to follow a small stimulus (ex. tip of the officer’s finger, penlight, pen, eraser of a pencil, etc.)
What the officer does: takes a small stimulus, holds it slightly above eye level about 12-15 inches away from your nose, and moves it horizontally from side-to-side checking for possible clues that could indicate you are under the influence
- The officer will check each eye for each of the 3 clues (listed below), meaning that there is a possibility of 6 total clues on the Horizontal Gaze Nystagmus test.
Clues:
- Lack of Smooth Pursuit (the eyes can be observed to jerk or bounce as they follow a smoothly moving stimulus)
- Distinct and Sustained Nystagmus at Maximum Deviation (when the eye is held at maximum deviation for a minimum of four seconds and continues to jerk toward the side)
- Onset of Nystagmus prior to 45 degrees (If the eye begins jerking prior to 45 degrees, it is evident the person has a BAC above 0.08.)
Walk-and-Turn Test (WAT) – a divided attention field sobriety test
What you are asked to do: follow the officer’s instructions, take nine heel-to-toe steps on the line, turn (keeping the lead foot on the line and turning by taking a series of small steps with the other foot), and take nine heel-to toe steps down the line
- Note: keep your arms at your sides, watch your feet at all times, count your steps out loud, and once you start walking don’t stop until you have completed the test
What the officer does: provides instructions, stands at a safe distance, and observes the test for clues of impairment
Clues:
- Cannot keep balance while listening to the instructions
- Starts too soon
- Stops while walking
- Does not touch heel-to-toe
- Steps off the line
- Uses arms for balance
- Improper turn
- Incorrect number of steps
One-Leg Stand Test (OLS) – a divided attention field sobriety test
What you are asked to do: raise your leg six inches off the ground while keeping your legs straight and arms at your side, count out “one thousand one,” “one thousand two,” etc. until told to stop
What the officer does: provides instructions, stands at a safe distance, times 30 seconds and discontinues the test after that time has passed, and observes the test for clues of impairment
Clues:
Puts foot down
The subject sways while balancing
Uses arms for balance
Hopping
Source: https://www.nhtsa.gov/sites/nhtsa.gov/files/2023-03/15911-SFST_Participant_Manual_2023-tag.pd
