Massachusetts DWI DUI OUI Field Sobriety Test Police Training Manual

maximum deviation for a minimum of four seconds. People exhibit slight jerking of the eye at maximum deviation, even when unimpaired, but this will not be evident or sustained for more than a few seconds. When impaired by alcohol, the jerking will be larger, more pronounced, sustained for more than four seconds, and easily observable.

• Onset of Nystagmus Prior To 45 Degrees (Clue Number Three)— The point at which the eye is first seen jerking. If the jerking begins prior to 45 degrees it is evident that the person has a BAC above 0.08, as shown by recent research.

The higher the degree of impairment, the sooner the nystagmus will be observable.

Estimating a 45-Degree Angle

It is important to know how to estimate a 45-degree angle. How far you position the stimulus from the suspect’s nose is a critical factor in estimating a 45-degree angle. (i.e., If the stimulus is held 12” in front of the suspect’s nose, it should be moved 12” to the side to reach 45 degrees. Likewise, if the stimulus is held 15” in front of the suspect’s nose, it should be moved 15” to the side to reach 45 degrees.)

For practice, a 45-degree template can be prepared by making a 15”-square cardboard and connecting its opposite corners with a diagonal line.

To use this device, hold it up so that the person’s
nose is above the diagonal line. Be certain that
one edge of the template is centered on the nose
and perpendicular to (or, at right angles to) the
face. Have the person you are examining follow a
penlight or some other object until suspect is looking
down the 45-degree diagonal. Note the position
of the eye. With practice, you should be able
to recognize this angle without using the template.

Specific Procedures

If the suspect is wearing eyeglasses, have them removed.

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