October 29, 2015

WI Detection and Standardized Field Sobriety Testing • Physiological • Gaze Neural Nystagmus

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
Physiological
Gaze
Neural Nystagmus
8-23
Physiological Nystagmus is a natural nystagmus that keeps the sensory cells of the eye
from tiring. It is the most common type of nystagmus. It happens to all of us, all the
time. This type of nystagmus produces extremely minor tremors or jerks of the eyes.
These tremors are usually too small to be seen with the naked eye. Physiological
nystagmus will have no impact on our Standardized Field Sobriety Tests, because it’s
tremors are usually invisible.
Gaze Nystagmus is a form of nystagmus that occurs when the eyes attempt to maintain
visual fixation on a stimulus.
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
Horizontal
Vertical
Resting
Gaze Nystagmus
8-24
For our purposes, gaze nystagmus is separated into three types:
• Horizontal
• Vertical
• Resting
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HS 178 R5/13 15 of 62
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
Involuntary jerking of the eyes, occurring
as the eyes gaze to the side
Observation of the eyes for Horizontal
Gaze Nystagmus provides the first and
most accurate test in the SFST Battery
It’s presence may indicate use of certain
other drugs
Horizontal Gaze Nystagmus
8-25
Horizontal Gaze Nystagmus is an involuntary jerking of the eyes, occurring as the eyes
gaze to the side. It is the observation of the eyes for Horizontal Gaze Nystagmus that
provides the first and most accurate test in the Standardized Field Sobriety Test battery.
Although this type of nystagmus is indicative of alcohol impairment, its presence may
also indicate use of certain other drugs.
Examples of other drugs are: CNS Depressants, Inhalants, and Dissociative Anesthetics
such as PCP and its analogs.
Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)
DWI Detection and Standardized Field Sobriety Testing
Involuntary jerking of the eyes (up and
down)
Occurs when the eyes gaze upward at
maximum elevation
Associated with high doses of alcohol and
certain other drugs
Drugs that cause VGN may cause HGN
Vertical Gaze Nystagmus
8-26
Vertical Gaze Nystagmus is an involuntary jerking of the eyes (up and down) which
occurs when the eyes gaze upward at maximum elevation. The presence of this type of
nystagmus is associated with high doses of alcohol for that individual and certain other
drugs. The drugs that cause Vertical Gaze Nystagmus are the same ones that cause
Horizontal Gaze Nystagmus.
There is no drug that will cause Vertical Gaze Nystagmus that may not cause Horizontal
Gaze Nystagmus. If Vertical Gaze Nystagmus is present and Horizontal Gaze
Nystagmus is not, it could be a medical condition.
For VGN to be recorded, it must be definite, distinct and sustained for a minimum of four
seconds at maximum elevation.
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HS 178 R5/13 16 of 62 Source: DWI Detection and
Standardized Field
Sobriety Testing
March 2013 Edition

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