Massachusetts DWI DUI OUI Field Sobriety Test Police Training Manual

(3) Resting Nystagmus is referred to as a jerking of the eyes as they look straight ahead. Its presence usually indicates a pathology or high doses of a drug such as PCP. If detected, take precautions. (OFFICER SAFETY.)

3. Nystagmus may also he caused by certain pathological disorders. They include brain tumors and other brain damage or some diseases of the inner ear. These pathological disorders occur in very few people and in even fewer drivers.

Medical Impairment

The examinations that you can conduct to assess possible medical impairment include:

• Resting Nystagmus
• Tracking ability
• Pupil size

PROCEDURES

Procedures to Assess Possible Medical Impairment

Prior to administration of HGN, the eyes are checked for equal tracking (can they follow an object together) and equal pupil size. If the eyes do not track together, or if the pupils are noticeably unequal in size, the chance of medical disorders or injuries causing the nystagmus is present. Resting Nystagmus may be observed at this time.

Procedures of Horizontal Gaze Nystagmus Testing: The Three Clues

The test you will use at roadside is “Horizontal Gaze Nystagmus”—an involuntary jerking of the eyes occurring as the eyes gaze toward the side. Some jerking will be seen if the eyes are moved far enough to the side.

• The Lack of Smooth Pursuit (Clue Number One)—The eyes can be observed to jerk or “bounce” as they follow a smoothly moving stimulus, such as a pencil or penlight. The eyes of an unimpaired person will follow smoothly, i.e., a marble rolling across a smooth pane of glass.
• Distinct Nystagmus At Maximum Deviation (Clue Number Two)—Distinct nystagmus will be evident when the eye is held at

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