Session
8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI
Detection and Standardized Field Sobriety Testing
Clue Number 3
Onset of Nystagmus Prior to 45 Degrees
8-51
Clue No. 3: Onset of Nystagmus Prior to 45 Degrees
Once
again, position the stimulus approximately 12 - 15 inches (30 - 38 cm) in front
of
subject's
nose and slightly above eye level.
The
angle of onset of nystagmus is simply the point at which the eye is first seen
jerking.
Examples:
With someone at a very high BAC (0.20+), the jerking might begin almost
immediately
after the eye starts to move toward the side. For someone at 0.08 BAC,
the
jerking might not start until the eye has moved nearly to the 45 degree angle.
Generally
speaking, the higher the BAC, the sooner the jerking will start as the eye
moves
toward the side.
If
the jerking begins prior to 45 degrees, that person’s BAC could be 0.08 or
above.
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Session
8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI
Detection and Standardized Field Sobriety Testing
Clue Number 3 (Cont.)
Onset of Nystagmus Prior to 45 Degrees
8-52
It
is not difficult to determine when the eye has reached the 45 degree point, but
it does
require
some practice.
If
you start with the stimulus approximately 12 - 15 inches (30 - 38 cm) directly
in front of
the
nose, you will reach 45 degrees when you have moved the stimulus an equal
distance
to the side. Two other important indicators can be used to determine if the eye
is
within 45 degrees.
At
45 degrees, some white usually will still be visible in the corner of the eye
(for most
people).
If
you started with the stimulus approximately 12 - 15 inches (30 - 38 cm) in
front of the
subject,
when you reach 45 degrees the stimulus will usually be lined up with, or
slightly
beyond,
the edge of the subject's shoulder.
Notes:_______________________________________________
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HS
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Session
8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI
Detection and Standardized Field Sobriety Testing
Mechanics of
Clue Number 3
8-53
The Mechanics of Clue No. 3
The
stimulus is positioned approximately 12 - 15 inches from (30 - 38 cm) subject's
nose
and slightly above eye level. It is necessary to move the stimulus slowly to
identify
the
point at which the eye begins to jerk.
Start
moving the stimulus towards the right side (left eye) at the speed that would
take
approximately
4 seconds for the stimulus to reach the edge of the subject's shoulder.
As
you are slowly moving the stimulus, watch the eye carefully for any sign of
jerking.
When
you see the jerking begin, immediately stop moving the stimulus and hold it
steady
at that position.
With
the stimulus held steady, look at the eye and verify that the jerking is
continuing.
If
the jerking is not evident with the stimulus held steady, you have not located
the point
of
onset. Therefore, resume moving the stimulus slowly toward the side until you
notice
the
jerking again.
When
you locate the point of onset of nystagmus, you must determine whether it is
prior
to
45 degrees.
Notes:_______________________________________________
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HS
178 R5/13 35 of 62
Session
8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI
Detection and Standardized Field Sobriety Testing
Mechanics of
Clue Number 3 (Cont.)
8-54
Verify
that some white is still showing in the corner of the eye.
Examine
the alignment between the stimulus and the edge of the subject's shoulder.
Start
moving the stimulus towards the left side (right eye) at the speed that would
take
approximately
4 seconds for the stimulus to reach the edge of the subject's shoulder.
As
you are slowly moving the stimulus, watch the eye carefully for any sign of
jerking.
When
you see the jerking begin, immediately stop moving the stimulus and hold it
steady
at that position.
With
the stimulus held steady, look at the eye and verify that the jerking is
continuing.
If
the jerking is not evident with the stimulus held steady, you have not located
the point
of
onset. Therefore, resume moving the stimulus slowly toward the side until you
notice
the
jerking again.
When
you locate the point of onset of nystagmus, you must determine whether it is
prior
to
45 degrees.
Verify
that some white is still showing in the corner of the eye.
Examine
the alignment between the stimulus and the edge of the subject's shoulder.
Session
8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI
Detection and Standardized Field Sobriety Testing
Live Demonstration
Clue Number 3
8-55
Live Demonstration of the Mechanics of Clue No. 3
Notes:_______________________________________________
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HS
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Session
8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI
Detection and Standardized Field Sobriety Testing
Participant Practice
Clue Number 3
8-56
Participant practice of the mechanics of Clue No. 3
Coaching
and critiquing participants practice.
Participant
led demonstration.
Session
8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI
Detection and Standardized Field Sobriety Testing
45 o
45 Degree Template
8-57
Training Aid: The 45 Degree Template
A
training aid has been provided to help you practice estimating a 45 degree
angle.
•
The outline of a square, with its diagonal line, gives us a 45 degree angle.
•
This outline, or template, is provided for practice only.
•
It is not to be used with actual DWI subjects.
To
use the template, have your training partner hold the corner of the square
under the
nose.
Notes:_______________________________________________
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HS
178 R5/13 37 of 62
Session
8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI
Detection and Standardized Field Sobriety Testing
45 Degree Template (Cont.)
45 o
8-58
When
you line up your stimulus with the diagonal line, your partner will be looking
along
a
45 degree angle.
Session
8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI
Detection and Standardized Field Sobriety Testing
Participant Practice
45 o
8-59
Coaching and Critiquing Participants' Practice
Participant led Demonstration
Session
8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI
Detection and Standardized Field Sobriety Testing
Horizontal Gaze Nystagmus
Test Criterion
4 or more clues indicates
BAC above 0.08 (88% accurate)
8-60
Test Interpretation
Based
upon the original developmental research into Horizontal Gaze Nystagmus, the
criterion
for this test is 4.
If
a person exhibits at least 4 out of the possible 6 clues, the implication is a
BAC above
0.08.
Using
this criterion, the test is 88% accurate.
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HS
178 R5/13 38 of 62
Standardized Field
Sobriety Testing
March 2013 Edition
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