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