DWI
Detection and Standardized Field Sobriety Testing
Session
7 – Phase Three: Pre-Arrest Screening
Involuntary Jerking of the Eyes
Nystagmus
7-7
B. Gaze Nystagmus – Definition
"Nystagmus"
means an involuntary jerking of the eyes.
Alcohol
and certain other drugs cause Horizontal Gaze Nystagmus.
DWI
Detection and Standardized Field Sobriety Testing
Session
7 – Phase Three: Pre-Arrest Screening
• Most
reliable field sobriety test
• Involuntary
jerking occurring as eyes
gaze toward the sides
• Readily
noticeable when a person is
impaired
• As
BAC increases eyes begin to jerk
sooner as they move to the side
• CNS
depressants, inhalants, and
dissociative anesthetics also cause
HGN
•
Horizontal Gaze Nystagmus (HGN)
7-8
C. Horizontal Gaze Nystagmus – Definition, Concepts, Demonstration
Horizontal
Gaze Nystagmus (HGN) is the most reliable field sobriety test. Especially
when
used in combination with the divided attention tests, it will help law
enforcement
officers
correctly identify subjects who are impaired.
Involuntary
jerking of the eyes becomes readily noticeable when a person is impaired.
As
a person's blood alcohol concentration increases, the eyes will begin to jerk
sooner
as
they move to the side.
Horizontal
Gaze Nystagmus refers to an involuntary jerking occurring as the eyes gaze
toward
the side. In addition to being involuntary the person experiencing the
nystagmus
is
usually unaware that the jerking is happening.
In
administering the HGN test, the officer has the subject follow the motion of a
small
stimulus
with the eyes only. The stimulus may be the tip of a pen or penlight, or an
eraser
on a pencil, whichever contrasts with the background.
Notes:_______________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
Notes:_______________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
HS
178 R5/13 5 of 26
No comments:
Post a Comment