Law Enforcement Caselaw and Statutes: DWI Detection and Standardized Field Sobriety Testing • Jerking of the eyes as they look straight ahead

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

• Jerking of the eyes as they look straight

ahead

• Presence usually indicates a pathological

disorder or high doses of a Dissociative

Anesthetic drug such as PCP

• If detected, take OFFICER SAFETY

precautions

Resting Nystagmus

8-27

Resting Nystagmus is referred to as a jerking of the eyes as they look straight ahead. Its

presence usually indicates a pathological disorder or high doses of a Dissociative

Anesthetic drug such as PCP. If detected, take precautions. (OFFICER SAFETY.)

Nystagmus may also be 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.

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

• Brain tumors and other brain damage

• Some inner ear diseases

• Rare in the driving population

Pathological Disorder Nystagmus

8-28

Nystagmus may also be 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.

Notes:_______________________________________________

_____________________________________________________

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 17 of 62

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

• Equal pupil size

• Resting nystagmus

• Equal tracking

Medical Impairment

8-29

Medical Impairment

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

• Equal pupil size

• Resting nystagmus

• Equal tracking

Pupil size will be affected by some medical conditions or injuries. If the two pupils are

distinctly different in size, it is possible that the subject:

• Has a prosthetic eye

• Is suffering from a head injury

• Has a neurological disorder

Resting nystagmus is referred to as jerking as the eyes look straight ahead. This

condition is not frequently seen. Its presence usually indicates a pathology or high

doses of a drug such as a Dissociative Anesthetic like PCP.

Resting nystagmus may also be a medical problem.

Tracking ability will be affected by certain medical conditions or injuries involving the

brain.

This observation is a medical assessment. If the two eyes do not track together, the

possibility of a serious medical condition or injury is present.

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 18 of 62

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

Even though the possibility of alcohol

and/or drug impairment exists, be aware of

medical conditions having symptoms in

common with alcohol influence.

Medical Impairment (Cont.)

8-30

By passing a stimulus across both eyes, you can check to see if both eyes are tracking

equally. If they don't (i.e., if one eye tracks the stimulus, but the other fails to move, or

lags behind the stimulus) there is the possibility of a neurological disorder.

If a person has sight in both eyes, but the eyes fail to track together, there is a possibility

that the person is suffering from an injury or illness affecting the brain.

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

• Check eyes for:

• Equal pupil size

• Resting nystagmus

• Equal tracking

• If eyes do not track together, or pupils are

noticeably unequal in size, medical disorders

or injuries may be present

HGN Medical Impairment

Assessment Procedures

8-31

Procedures to Assess Possible Medical Impairment

Prior to administration of HGN, the eyes are checked for equal pupil size, resting

nystagmus, and equal tracking (can they follow an object together). 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 may be present.

Notes:_______________________________________________

_____________________________________________________

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 19 of 62

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

• Lack of smooth pursuit

• Distinct and sustained Nystagmus at

maximum deviation

• Onset of Nystagmus prior to 45 degrees

HGN Testing: Three Clues

8-32

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 to the side. When a person is impaired

by alcohol or certain drugs, 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 impaired person will not follow smoothly, i.e., a marble rolling across sand

paper, or windshield wipers moving across a dry windshield.

• Distinct and Sustained Nystagmus At Maximum Deviation (Clue Number Two) -

Distinct and sustained nystagmus is evident when the eye is held at maximum

deviation for a minimum of four seconds and continues to jerk toward the side.

• 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.

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 20 of 62

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

• Check for eyeglasses

• Verbal instructions

• Position stimulus (12-15 inches and slightly above

eye level)

• Check for equal pupil size and resting nystagmus

• Check for equal tracking

• Lack of smooth pursuit

• Distinct and sustained nystagmus at maximum

deviation

• Onset of nystagmus prior to 45 degrees

• Total the clues

• Check for vertical nystagmus

Administrative Procedures

8-33

Horizontal and Vertical Gaze Nystagmus can be observed directly and does not require

special equipment. You will need a contrasting stimulus for the subject to follow with

their eyes. This can be a penlight or pen. The stimulus used should be held slightly

above eye level, so that the eyes are wide open when they look directly at it. It should

be held approximately 12 - 15 inches in front of the nose. Remain aware of your position

in relation to the subject at all times.

• Check for eyeglasses

• Verbal instructions

• Position stimulus (12-15 inches and slightly above eye level)

• Check for equal pupil size and resting nystagmus

• Check for equal tracking

• Lack of smooth pursuit

• Distinct and sustained nystagmus at maximum deviation

• Onset of nystagmus prior to 45 degrees

• Total the clues

• Check for vertical nystagmus

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 21 of 62

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

1. Check for eyeglasses

HGN Procedures

8-34

Administrative Procedures for Horizontal Gaze Nystagmus

It is important to administer the Horizontal Gaze Nystagmus test systematically using

the following steps, to ensure that nothing is overlooked.

There are 10 steps in the systematic administration of the Horizontal Gaze Nystagmus

test.

Step 1: Check for Eyeglasses.

Begin by instructing the subject to remove eyeglasses, if worn.

It does not matter whether the subject can see the stimulus with perfect clarity, as long

as subject can see it at all.

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 22 of 62

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

1. Check for eyeglasses

2. Verbal instructions

3. Position stimulus

HGN Procedures (Cont.)

8-35

Step 2: Verbal Instructions.

Give the subject the appropriate verbal instructions:

Point out that officers’ should note whether subject sways, wobbles, etc. while trying to

balance.

• Put feet together, hands at the side

• Keep head still

• Look at the stimulus

• Follow movement of the stimulus with the eyes only

• Keep looking at the stimulus until told the test is over

Step 3: Position the Stimulus.

Position the stimulus approximately 12 - 15 inches (30 - 38 cm) in front of subject's

nose, and slightly above eye level to commence the test.

Resting Nystagmus may be observed at this time. Officers should note whether the

subject displays Resting Nystagmus.

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 23 of 62

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

4. Pupil size and resting nystagmus

5. Equal tracking

HGN Procedures (Cont.)

8-36

Step 4: Equal Pupil Size and Resting Nystagmus. Check for equal pupil size and

resting nystagmus.

Step 5: Equal Tracking.

Check for equal tracking. Move the stimulus rapidly from center to far right, to far left

and back to center.

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

6. Check for lack of smooth pursuit

7. Check for distinct and sustained

nystagmus at maximum deviation

8. Check for onset of nystagmus prior to 45

degrees

HGN Procedures (Cont.)

8-37

Step 6: Lack of Smooth Pursuit. Check the left eye for lack of the "Smooth Pursuit"

clue. If the eye is observed to jerk while moving, that is one clue.

Check the right eye for lack of the "Smooth Pursuit" clue and compare.

Step 7: Check the right and left eye for the "distinct and sustained nystagmus at

maximum deviation" clue. If the jerkiness is distinct and sustained, that is one clue.

Step 8: Onset of Nystagmus Prior to 45 Degrees. Check the left eye for the "onset of

nystagmus prior to 45 degrees" clue. If the jerking begins prior to 45 degrees, that is

one clue.

Check the right eye for "onset of nystagmus prior to 45 degrees" clue, and compare.

Notes:_______________________________________________

_____________________________________________________

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 24 of 62

HS 178 R5/13 25 of 62

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

9. Total the clues

10. Check for Vertical Gaze Nystagmus

HGN Procedures (Cont.)

8-38

Step 9: Total the clues

Maximum number of clues possible for each eye: 3

Total maximum number of clues possible for both eyes: 6.

Step 10: Check for Vertical Nystagmus

It is possible that all three clues definitely will be found in one eye, while only two (or

sometimes only one) will show up in the other eye. It is always necessary to check both

eyes, and to check them independently. Notwithstanding, it is unlikely that the eyes of

someone under the influence of alcohol will behave totally different.

Thus, if one eye shows all three clues distinctly while the other eye gives no evidence of

nystagmus, the person may be suffering from one of the pathological disorders covered

previously.

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 26 of 62

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

Look for three clues of nystagmus in each

eye:

• Lack of smooth pursuit

• Distinct and sustained Nystagmus at

maximum deviation

• Onset of Nystagmus prior to 45 degrees

Test Interpretation

8-39

Test Interpretation

You should look for three clues of nystagmus in each eye.

Lack of Smooth Pursuit (The eye cannot follow a moving object smoothly)

Distinct and Sustained Nystagmus at Maximum Deviation (Nystagmus is distinct and

sustained when the eye is held at maximum deviation for a minimum of four seconds)

Onset of Nystagmus Prior to 45 Degrees.

Based on recent research, if you observe four or more clues it is likely that the subject's

BAC is at or above 0.08. Using this criterion you will be able to classify about 88% of

your subjects accurately. This was determined during laboratory and field testing and

helps you weigh the various Standardized Field Sobriety Tests in this battery as you

make your arrest decision.

Session 8 - Concepts and Principles of the Standardized Field Sobriety Tests (SFST)

DWI Detection and Standardized Field Sobriety Testing

• Lack of smooth pursuit

• Distinct and sustained nystagmus at

maximum deviation

• Onset of nystagmus prior to 45 degrees

Three Clues of Horizontal Gaze

Nystagmus

8-40

When we administer the Horizontal Gaze Nystagmus test, we look for three specific

clues as evidence of alcohol influence.

We check each eye independently for each clue.

For standardization, begin with the subject's left eye. Check for the first clue. Next,

check right eye for same clue. Repeat this procedure for each clue starting with left

eye, then right eye. Compare and document the results.

When we are checking an eye, it is good practice to administer the test by the numbers

each time, to make sure that no step is overlooked.

Notes:_______________________________________________

_____________________________________________________

Notes:_______________________________________________

_____________________________________________________

HS 178 R5/13 27 of 62 Source: DWI Detection and

Standardized Field

Sobriety Testing

March 2013 Edition

Law Enforcement Caselaw and Statutes

October 29, 2015

DWI Detection and Standardized Field Sobriety Testing • Jerking of the eyes as they look straight ahead

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