Field Sobriety Test FAQs
Field sobriety tests measure a person’s physical or mental impairment, and focus on the abilities needed for safe driving. The more reliable types of tests are called “divided attention” tasks, and require a person to focus on more than one thing at the same time. When driving, you must be able to control multiple parts of the vehicle while staying alert to react to the environment. Alcohol affects your ability to effectively divide this attention.
A good field sobriety test will be relatively simple for the average sober person to perform, and should combine at least two of the following elements:
- Short-term memory
- Information processing
- Decision-making and judgment
- Balance
- Reactions
- Vision
- Limb coordination
- Small muscle control
The three most common standardized field sobriety tests are the horizontal gaze nystagmus test, walk and turn test, and the one leg stand test.
Horizontal Gaze Nystagmus
In this test, the officer holds a stimulus – usually a pen – 12 to 15 inches in front of your face and asks you to follow it with your eyes without moving your head. The officer is looking for:
- Do your eyes follow smoothly or do they jerk?
- When your eye is all the way to the side, does it bounce?
- Does the eye start to jerk before the pen reaches a 45-degree angle?
This test is shown to be accurate 77% of the time.
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Walk and Turn Test
During the instruction phase, you must stand with your right foot in front of your left foot, heel and toes touching, arms at your sides. You will listen while the officer recites instructions for 45 seconds. If you use your arms for balance or step out of the position, this is a sign of intoxication.
During the walking phase, you will take 9 heel-to-toe steps, turn, then take the same steps back while counting them out loud. The steps are taken down a line, or an imaginary line if one is not present. Signs of intoxication include:
- Loss of balance during instructions
- Starting too soon
- Stopping while walking
- Not walking heel-to-toe
- Stepping off the line
- Using your arms for balance
- Losing your balance while turning
- Taking the wrong number of steps
If two or more of these signs are present, the officer should assume you are intoxicated. This test is correct 68% of the time.
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One Leg Stand
During the instruction phase, you must stand with your feet together and arms at your sides. During the next phase, you must raise one leg about six inches off the ground while keeping your arms at your sides, pointing your toes out, looking at your toes, and keeping both legs straight. You are then supposed to count while looking at your toes until the officer tells you to stop, which should be 30 seconds. If you put your foot down, the officer will instruct you to pick your foot back up and keep counting.
Two or more of these clues are signs of intoxication:
- Swaying
- Using your arms for balance
- Hopping
- Putting your foot down
This test is 65% accurate.
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