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

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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

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In the Instruction Stage, the subject must stand with their feet together, keep their arms

at their sides, and listen to instructions.

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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

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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.

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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.

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HS 178 R5/13 16 of 26 Source: DWI Detection and

Standardized Field

Sobriety Testing

March 2013 Edition