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es from the subject’s nose, and slightly above the eyes. Pri- or to conducting the HGN, subjects should remove their eyeglasses. Contacts are OK.
Begin the HGN test with a medical assessment, check- ing for the following:
• Resting Nystagmus (are the eyes jerking as they look forward toward the stimulus). If present, it can indicate the presence of a dissociative anesthetic, such as PCP.
• Equalpupilsize:Unequalpupilscanindicateaheadin- jury or prosthetic eye.
• Equal tracking. Are both eyes following the stimulus at the same time? If there is a lack of smooth pursuit, you might ask the subject, “Did you know your left eye is not following me?” The subject might respond, “I have a lazy eye.” Considine reasons that you are now aware of a medical condition that might affect a person’s test.
• Upon concluding the medical assessment, officers are required to stop and take a distinctive break to prevent eye fatigue that could be misinterpreted as nystagmus.
• Next, look for three distinctive clues in each eye: lack of smooth pursuit, distinct and sustained nystagmus at maximum deviation and the onset of nystagmus prior to 45 degrees.
• To check for lack of smooth pursuit, bring the stimu- lus to slightly above the eyes, 12 to 15 inches away from the nose. Look for inability to hold the eyes steady on a moving target. Is the eye following smoothly or is there a distinct jerkiness?
• Move the stimulus to the right, checking the subject’s left eye first, then back across to check the right eye. Two full passes are required by NHTSA.
• Immediately after the second pass, check for “distinct and sustained nystagmus at maximum deviation.” Again, starting with the left eye, move the stimulus to the point where no white can be seen in the far corner of the eye. “Look for a distinct jerking, which must be sustained for a minimum of four seconds,” Considine notes. “Anything less than four seconds and the clue is not present.”
• Aftercheckingthelefteye,movethestimulusacrossthe subject’s face to check for the same distinctive jerking in the right eye. A complete second pass over both eyes is required.
• When checking for the third clue – onset of nystagmus prior to 45 degrees – officers are looking to see when the eye first begins to jerk. This is done by slowly moving the stimulus 12 to 15 inches outward, starting with the subject’s left eye. Slowly move the stimulus to the right (checking the subject’s left eye), taking at least four sec- onds to reach 45 degrees (some white should be seen in the far corner of the subject’s eye). If jerking is observed prior to 45 degrees, stop, confirm the jerking and check the subject’s right eye. If eye jerking is observed at or beyond what is estimated to be 45 degrees, the clue is not present. A second full pass is required by NHTSA.
• After checking for the third clue, look for Vertical Gaze Nystagmus (VGN), which is part of the administrative procedures set forth by NHTSA. Hold the stimulus hor- izontally, 12 to 15 inches away from the subject’s nose and slightly above the eyes. Raise the stimulus as high as the eyes will look up. When the subject is looking up, the officer is looking for the downward jerking of the eyes. If downward jerking is observed, it must be sus-
tained for a minimum of four seconds. VGN is not a val- idated clue but an indication of “high concentrations” of a central nervous system depressant, such as alcohol.
“If an officer sees a minimum of four clues (from a maxi- mum of six clues), it is an indication with 88 percent accu- racy that this person is .08 or greater,” Considine presents.
Prior to administering the Walk and Turn or One Leg Stand tests, officers should ask subjects if there are any reasons they are unable to perform either one. NHTSA re- quires asking the subject for any physical limitations that would prevent taking a field test.
During the WAT, follow the administrative procedures set by NHTSA. Officers should give the instructions verbal- ly, physically demonstrate what is required and ask if the subject understands the instructions. Look for any of the eight clues that indicate impairment during the subject’s performance of the WAT:
• Unable to maintain balance while listening to instruc- tions.
• Starts too soon.
• Stops walking to maintain balance.
• Does not touch to heel-to-toe (with a half-inch or more
of separation).
• Steps off the line.
• Uses arms for balance (six inches or more).
• Incorrect number of steps.
• Improper turn.
“If a subject displays two individual clues or more, it in- dicates with 79-percent accuracy that the person is .08 or greater,” Considine states.
With the OLS, NHTSA requires the subject to raise the leg of choice. The foot of the raised leg should be a minimum of six inches off and parallel to the ground. The raised and planted legs must both be straight. Have the subject count out loud, “1000-1, 1000-2, 1000-3” in that position until told to stop.
During the OLS, look for any of the four clues that indi- cate impairment during the subject’s performance:
• Swaying (arms, body, raised leg/foot).
• Using arms for balance (six inches or more away from
the body).
• Hopping (resorting to lifting the planted leg to prevent
falling or losing balance).
• Putting foot down.
“In the OLS, two clues or more indicate with 83-percent accuracy that the subject is .08 or greater,” Considine doc- uments.
In addition to accounting for safety, officers should re- member that there is no time limit on the field test. So take your time to get it right, because Considine emphasizes that getting it right will make the difference in court.
Considine confides that some detectives would rather deal with homicides than DUI because of the attorneys and the time spent in court testifying. But think of all the lives you can save with one DUI stop and arrest. Think of how many you can save with 10!
“That’s really what DUI is about,” Considine concludes. “Take good notes, put together well written, articulate re- ports and your testimony will be that much better. DUI is about the identifying and gathering of all evidence from all three phases to base your decision on whether to arrest.”d
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