October 29, 2015

DWI Detection and Standardized Field Sobriety Testing One Leg Stand Divided Attention Test

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
One Leg Stand
Divided Attention Test
Mental Task and Physical Task
Instructions stage
Balance and counting stage
8-80
F. One Leg Stand
Test Stages
Like all divided attention tests, One Leg Stand has two stages.
They are:
• Instructions stage
• Balance and counting stage
Both stages are important, because they can affect the subject's overall performance on
the test.
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HS 178 R5/13 49 of 62
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
One Leg Stand
8-81
Test Conditions
One Leg Stand requires a reasonably dry, hard, level, and non-slippery surface.
Subject's safety should be considered at all times.
Standardizing this test for every type of road condition is unrealistic. The original
research study recommended that this test be performed on a dry, hard, level, nonslippery
surface and relatively safe conditions. If not, the research recommends:
• subject be asked to perform the test elsewhere, or
• only HGN be administered
However, recent field validation studies have indicated that varying environmental
conditions have not affected a subject’s ability to perform this test.
The original SCRI studies suggested that individuals over 65 years of age; people with
back, leg or inner ear problems; or people who are overweight by 50 or more pounds
may have difficulty performing this test. Less than 1.5% of the test subjects in the
original studies were over 65 years of age. There was no data containing the weight of
the test subjects included in the final report. Also, the SCRI studies suggest that
individuals wearing heels more than 2 inches high should be given the opportunity to
remove their shoes.
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
One Leg Stand
8-82
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HS 178 R5/13 50 of 62
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
Administrative Procedures
Instructions stage:
Stand straight, feet together
Keep arms at sides
Maintain position until told otherwise
8-83
Instructions Stage: Initial Positioning and Verbal Instructions
Initiate the test by giving the following instructions, accompanied by demonstrations.
Please stand with your feet together and your arms down at the sides, like this.
Do not start to perform the test until I tell you to do so.
Do you understand the instructions so far?
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
Administrative Procedures
(Cont.)
Balance and counting stage:
Raise either leg
Keep raised foot approximately six inches
(15 cm) off ground
Keep both legs straight and arms at your
side
Keep eyes on raised foot
Count out loud in the following manner:
“one thousand one, one thousand two, one
thousand three and so on”, until told to
stop
8-84
Demonstrations and Instructions for the Balance and Counting Stage
Explain the test requirements, using the following verbal instructions, accompanied by
demonstrations:
When I tell you to start, raise either leg with the foot approximately six inches off the
ground.
Keep both legs straight and your arms at your side.
While holding that position, count out loud in the following manner: “one thousand one,
one thousand two, one thousand three,” and so on until told to stop.
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HS 178 R5/13 51 of 62
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
Administrative Procedures
(Cont.)
Balance and counting stage:
Raise either leg
Keep raised foot approximately six inches
(15 cm) off ground, foot pointed out
Keep both legs straight and arms at your
side
Keep eyes on raised foot
Count out loud in the following manner:
“one thousand one, one thousand two, one
thousand three and so on”, until told to
stop
8-85
Keep your arms at your sides at all times and keep watching the raised foot.
Do you understand?
Go ahead and perform the test. (Officer should always time the 30 seconds. Test should
be discontinued after 30 seconds.)
Observe the subject from a safe distance. If the subject puts the foot down, give
instructions to pick the foot up again and continue counting from the point at which the
foot touched the ground. If the subject counts very slowly, terminate the test after 30
seconds.
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
One Leg Stand Test Clues
Sways while balancing
Uses arms to balance
Hopping
Puts foot down
8-86
Test Interpretation
You may observe a number of different behaviors when a subject performs this test. The
original research found the behaviors listed below are the most likely to be observed in
someone with a BAC at or above 0.08. When administering the One Leg Stand test, we
look for certain specific behaviors. Each behavior or action is considered one clue.
There is a maximum number of 4 clues on this test. Look for the following clues each
time the One leg Stand test is administered.
The subject sways while balancing. This refers to side to side or back and forth motion
while the subject maintains the one leg stand position.
Slight tremors of the foot or body should not be interpreted as swaying.
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HS 178 R5/13 52 of 62
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
One Leg Stand Test Clues
Sways while balancing
Uses arms to balance
Hopping
Puts foot down
8-87
Uses arms to balance. Subject moves arms 6 or more inches from the side of the body
in order to keep balance.
Hopping. Subject is able to keep one foot off the ground, but resorts to hopping in order
to maintain balance.
Puts foot down. The subject is not able to maintain the one leg stand position, putting
the foot down one or more times during the 30 second count.
If the subject puts the foot down, give instructions to pick the foot up again and continue
counting from the point at which the foot touched.
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
One Leg Stand Test Clues
Sways while balancing
Uses arms to balance
Hopping
Puts foot down
8-88
If subject can't do the test, record observed clues and document the reason for not
completing the test, e.g. subject’s safety.
Remember that time is critical in this test. The original SCRI research has shown a
person with a BAC above 0.10 can maintain balance for up to 25 seconds, but seldom
as long as 30.
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HS 178 R5/13 53 of 62
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
One Leg Stand Test Criterion
2 or more clues indicates BAC
at or above 0.08 (83% accurate)
8-89
Based on recent research, if an individual shows two or more clues or fails to complete
the One Leg Stand, there is a good chance the BAC is at or above 0.08. Using that
criterion, you will accurately classify 83% of the people you test as to whether their
BAC's are at or above 0.08.
Observe the subject from a safe distance and minimize movement during the test so as
not to interfere. If the subject puts the foot down, give instructions to pick the foot up
again and continue counting from the point at which the foot touched the ground. If the
subject counts very slowly, terminate the test after 30 seconds.
Review of Divided Attention Definition
One Leg Stand is another field sobriety test that employs divided attention.
The subject's attention is divided among such simple tasks as balancing, listening, and
counting out loud.
Although none of these is particularly difficult in itself, the combination can be very
difficult for someone who is impaired.
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
One Leg Stand Test
Demonstration
8-90
Test Demonstrations
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HS 178 R5/13 54 of 62 Source: DWI Detection and
Standardized Field
Sobriety Testing
March 2013 Edition

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