DWI
Detection and Standardized Field Sobriety Testing
Session
7 – Phase Three: Pre-Arrest Screening
• Six
maximum clues
• Maximum
three clues per eye
• 77%
accurate detecting subjects
≥ 0.10 BAC
Nystagmus Indications
7-9
•
When the HGN test is administered always begin with subject's left eye. Each
eye is
examined
for three specific clues.
•
As the eye moves from side to side, does it move smoothly or does it jerk
noticeably?
(As
people become impaired by alcohol, their eyes exhibit a lack of smooth pursuit
as
they
move from side to side.)
•
When the eye moves as far to the side as possible and is kept at that position
for four
seconds,
does it jerk distinctly? (Distinct and sustained nystagmus at maximum
deviation
is another clue of impairment.)
•
As the eye moves toward the side, does it start to jerk prior to a 45 degree
angle?
(Onset
of nystagmus prior to 45 degrees is another clue of impairment.)
•
As a person's blood alcohol concentration increases it is more likely these clues
will
appear.
•
The maximum total number of clues is six. The maximum number of clues that may
appear
in one eye is three.
•
The original research was conducted by the Southern California Research
Institute
(SCRI)
and used to develop the initial curriculum showing this test was 77% accurate
at
detecting subjects at or above a 0.10 BAC.
Notes:_______________________________________________
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HS
178 R5/13 6 of 26
Source: DWI Detection and
Standardized Field
Sobriety Testing
March 2013 Edition
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