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Overview of Standard Field Sobriety Testing (SFST)

Field Sobriety Tests are basically psycho-physical tests administrated by law enforcement officers when an individual is suspected of DWI. Field sobriety tests can vary from jurisdiction to jurisdiction nationwide. Some of these tests consist of reciting the alphabet backwards, counting backwards, and finger counting. However, the most accepted field sobriety tests are the three Standard Field Sobriety Tests (SFST). According to the National Highway Traffic Safely Administration (NHTSA), the SFST are scientifically validated tests that if administrated correctly are reliable in predicting whether an individual’s blood alcohol content (BAC) is greater than 0.10%. These three tests are the One-Leg Stand, Walk and Turn, and the Horizontal Gaze Nystagmus (HGN) test.

One-Leg Stand: According to the NHTSA, if instructed properly, the one leg stand test has a 65% reliability of predicting that an individual’s BAC is 0.10% or greater. An individual that is administered the one leg stand test must be properly instructed by the officer as follows:

  1. Stand with your feet together and your arms at your side 2. Keep that position until you are told to begin 3. The officer must ask if you understand the instructions and receive an acknowledgment from you that you do. 4. When told to start, raise either leg approximately 6 inches off the ground with your foot pointed out 5. Keep both legs straight, arms at side 6. Count 1,1000, 2, 1000, etc until officer instructs you to stop 7. Keep your arms at side and keep watching your raised foot 8. The officer must again ask if you understand the instructions and receive an acknowledgment from you that you do 9. The officer must then start the test 10. The test can last no longer than 30 seconds of actual time.

There are four scoring factors (clues) that officers look for when administering the one-leg stand test:

  1. Sways while balancing 2. Uses arms for balance 3. Hopping 4. Puts foot down

Inability to complete the test occurs when an individual:

  1. Puts foot down three or more times, during the 30-second period; or 2. Cannot perform the test.

Walk and Turn Test: According to the NHTSA, if instructed properly, the walk and turn has a 68% reliability of predicting that an individual’s BAC is 0.10% or greater when there or two or more “clues" indicated, or the test cannot be completed. An officer must properly instruct an individual, and the officer must demonstrate the following:

  1. Place your left foot on the line 2. Place your right foot on the line ahead of your left foot, with the heel of your right foot against toe of your left foot 3. Keep your arms to your side 4. Keep this position until you are told to begin 5. The officer must ask if you understand the instructions and receive an acknowledgment from you that you do. 6. When told to start, take 9 heel-to-toe steps, turn, and take 9 heel-to-toe steps back 7. When you turn, keep the front foot on the line, and turn by taking a series of small steps with the other foot 8. While walking, keep arms at side, watch feet at all times, and count steps out loud 9. Once you start, don’t stop until test is completed 10. The officer must ask if you understand the instructions and receive an acknowledgment from you that you do. 11. Begin the test and count first step from the heel-to-toe as “one".

There are eight scoring factors (clues) that an officer is observing for the Walk and Turn test:

  1. Cannot keep balance while listening to instructions 2. Starting before instructions are finished 3. Stopping while walking 4. Did not touch heel-to-toe 5. Stepped off line 6. Used arms for balance 7. Improper turn 8. Incorrect number of steps Horizontal Gaze Nystagmus (HGN) test: According to the NHTSA, if properly instructed, the HGN test is the most reliable SFST of predicting that an individual’s BAC is 0.10% or greater. The HGN test is said to be reliable 77%, if four or more “clues" are present. An officer must instruct an individual the following:

  2. I am going to check your eyes 2. Keep your head still and follow the stimulus (usually a pen or officer’s finger) with your eyes only 3. Keep following the stimulus with your eyes until the officer tells you to stop.

There are six scoring factors for the HGN test (one for each eye):

  1. The Lack of Smooth Pursuit; do the eyes bounce as they follow a smoothly moving stimulus. 2. Distinct Nystagmus at Maximum Deviation; distinct nystagmus will be evident when the eye is held at maximum deviation for a minimum of four seconds 3. Onset of Nystagmus at Prior to 45 Degrees; officer is observing for the point at which the eye is first observed jerking.

Important tips regarding SFSTs:

  1. An individual has a Right to Refuse to submit to these tests. 2. Any field sobriety testing must be fair and must be strictly administrated according to the NHTSA standards. 3. A sober person can fail the SFSTs, thus a failing grade on any of the SFSTs is not always an indication of intoxication. In fact, there may be several factors that contributed to failing the SFSTs that the officer failed to account for when administrating the tests, such as underlying medical, mental, and physical disorders. 4. An DWI attorney may be able to challenge the validity and reliability of any field sobriety testing.

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