October 29, 2015

DWI Detection and Standardized Field Sobriety Testing Session 7 – One Leg Stand Phase Three: Pre-Arrest Screening • Validated by NHTSA

DWI Detection and Standardized Field Sobriety Testing
Session 7 – Phase Three: Pre-Arrest Screening
Validated by NHTSA
65% accurate at detecting subjects 0.10
BAC
Two stages:
1. Instructions Stage
2. Balance and Counting
Stage
One Leg Stand
7-21
One Leg Stand
The One Leg Stand has also been validated through NHTSA sponsored research.
The original research was conducted by the SCRI and used to develop the initial
curriculum showing this test was 65% accurate at detecting subjects at or above a 0.10
BAC.
It is a divided attention test consisting of two stages:
• Instructions stage
• Balance and counting stage
DWI Detection and Standardized Field Sobriety Testing
Session 7 – Phase Three: Pre-Arrest Screening
Divides driver's attention:
Balancing task
Information
processing
One Leg Stand – Instruction Stage
7-22
In the Instruction Stage, the subject must stand with their feet together, keep their arms
at their sides, and listen to instructions.
Notes:_______________________________________________
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HS 178 R5/13 14 of 26
DWI Detection and Standardized Field Sobriety Testing
Session 7 – Phase Three: Pre-Arrest Screening
Divides subject’s attention:
Balancing task
Small muscle control
30 second timing is important!
Balancing and Counting Stage
7-23
In the Balance and Counting Stage, the subject must raise one foot, either foot, with the
raised foot approximately six inches off the ground, with both legs straight and the
raised foot parallel to the ground. While looking at the elevated foot, count out loud in
the following manner: "one thousand one", "one thousand two", “one thousand three”
until told to stop. This divides the subject's attention between balancing (standing on
one foot) and small muscle control (counting out loud).
The timing for a thirty second period by the officer is an important part of the One Leg
Stand test. The original research conducted by SCRI in 1977 showed that many
impaired subjects are able to stand on one leg for up to 25 seconds, but that few can do
so for 30 seconds.
Notes:_______________________________________________
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HS 178 R5/13 15 of 26
DWI Detection and Standardized Field Sobriety Testing
Session 7 – Phase Three: Pre-Arrest Screening
Four clues:
1. Sways while balancing
2. Uses arms to balance
3. Hopping
4. Puts foot down
One Leg Stand
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One Leg Stand is also administered and interpreted in a standardized manner. Officers
carefully observe the subject's performance and look for four specific clues:
• Sways while balancing
• Uses arms to balance
• Hopping
• Puts foot down
Inability to complete the One Leg Stand test occurs when the subject is in danger of
falling or otherwise cannot complete the test.
Notes:_______________________________________________
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HS 178 R5/13 16 of 26 Source: DWI Detection and
Standardized Field
Sobriety Testing
March 2013 Edition

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