If you're pulled over on suspicion of drunk driving, an officer may ask you to perform field sobriety tests (FSTs). Understanding what these tests involve and your rights regarding them can significantly impact your case.
The Three Standardized Field Sobriety Tests
The National Highway Traffic Safety Administration (NHTSA) has established three standardized tests that officers use to assess impairment:
1. Horizontal Gaze Nystagmus (HGN)
The officer moves a stimulus (usually a pen or finger) side to side while watching your eyes. They're looking for:
- Inability to smoothly follow the object
- Distinct jerking of the eye at maximum deviation
- Eye jerking starting within 45 degrees of center
This test is considered the most reliable but can be affected by medical conditions, medications, and environmental factors.
2. Walk-and-Turn Test
You'll be asked to take nine heel-to-toe steps along a straight line, turn, and take nine steps back. Officers look for eight clues:
- Can't balance during instructions
- Starting before instructions finish
- Stopping while walking
- Not touching heel-to-toe
- Stepping off the line
- Using arms for balance
- Improper turn
- Wrong number of steps
3. One-Leg Stand Test
You'll be asked to stand on one foot with the other foot about six inches off the ground while counting for 30 seconds. Officers watch for:
- Swaying while balancing
- Using arms for balance
- Hopping
- Putting foot down
According to NHTSA's own research, these tests are not 100% accurate. The HGN test is about 77% accurate, walk-and-turn about 68%, and one-leg stand about 65%. Many factors beyond alcohol can cause "failure."
Do You Have to Take Field Sobriety Tests?
In most states, field sobriety tests are voluntary. Unlike chemical tests (breathalyzer, blood draw), there's typically no legal penalty for politely refusing to perform FSTs.
However, there are considerations:
- Refusing may lead to arrest anyway if the officer has other evidence of impairment
- Your refusal can be mentioned in court
- Performing poorly can provide additional evidence against you
Factors That Affect Test Performance
Many factors unrelated to alcohol can cause poor performance:
- Medical conditions: Inner ear disorders, leg or back injuries, neurological conditions
- Age and weight: Tests are harder for older or heavier individuals
- Footwear: High heels or uncomfortable shoes
- Weather: Wind, rain, cold temperatures
- Road conditions: Uneven surfaces, gravel, slopes
- Lighting: Poor visibility, flashing police lights
- Nervousness: Anxiety from the traffic stop
- Medications: Certain prescriptions affect balance and eye movement
Non-Standardized Tests
Officers sometimes use additional tests that are not NHTSA-approved:
- Finger-to-nose test
- Counting backwards
- Reciting the alphabet
- Finger counting
These non-standardized tests have not been scientifically validated and can be challenged more easily in court.
How Tests Can Be Challenged
An experienced DUI attorney may challenge field sobriety test results based on:
- Improper administration by the officer
- Inadequate training of the officer
- Environmental conditions during testing
- Your medical conditions or physical limitations
- Lack of video evidence
- Failure to provide proper instructions
Charged After Field Sobriety Tests?
An experienced DUI attorney can review how tests were administered and build your defense.
Find a DUI Attorney →What to Remember
- Field sobriety tests are generally voluntary
- You can politely decline without automatic penalties
- Many factors besides alcohol affect performance
- Test results can often be challenged in court
- Chemical tests (breath/blood) have different rules than FSTs
- Always consult an attorney if charged with DUI