Traffic Violations

Standard Field Sobriety Tests Part III: Optical Intoxication Signs

This is the third installment of a 10-part series on Standard Field Sobriety Tests.  In the first two blogs, we looked at HGN (horizontal gaze nystagmus) and optical medical conditions and how they can affect the outcome of a field sobriety test.  Continuing where we left off the last time, we will now take a look at optical signs of drunkenness.  In intoxication, three signs will often be observed, and to accurately test for this each eye must be checked separately.

The first clue that is looked for is known as smooth pursuit. What the officer is trained to look for is the suspect’s inability to pursue a moving stimulus smoothly while focusing on that stimulus while it is being moved horizontally and then from side to side.  If the suspect moves his or her head to the side at any time, the score may be invalid regardless of which clue they are looking for.  An example of what is being looked for is a movement like a marble rolling across a smooth pane of glass.  This will be a very smooth pursuit.

If the suspect is under the influence, the eyes will bounce or jerk in similar fashion as that same marble being rolled across a piece of sandpaper.  The officer is instructed to check the left eye first by moving the object to the officer’s right.  The object must be moved smoothly, at a speed of about two seconds to bring the suspect’s eye as far to the side as it can go.  Any choppy or shaky hand movements, or moving too may induce a nystagmus in the suspect’s eyes and invalidate the scoring and test.

The officer is instructed to make two or more passes in front of the eye to be absolutely certain that what they are seeing is nystagmus.  If this clue is scored as nystagmus, the suspect is assessed one point.  If the suspect has this clue emanating in one eye, it is no guarantee that it will be exhibited in the other eye.  This should be the easiest clue to see.

After they have checked the first eye for the smooth pursuit clue, they must check the same eye for what is called distinct and sustained nystagmus at maximum deviation.  This is accomplished by simply moving the object until the eye has gone as far to the side as possible.  At maximum deviation, no sclera or white will be showing in the corner of the eyeball. The officer must hold the eyeball at that position for four seconds.

In this context, distinct nystagmus means that the jerky movement is greater than nystagmus observed when testing for smooth pursuit.  “Sustained Nystagmus” means that the movement must be observed continuously for at least four seconds.  The nystagmus must be both distinct and obvious.

If the officer cannot make this distinction from a slight nystagmus, the benefit of the doubt must be given the suspect.  The officer may make the mistake of not bringing the eyes out to side as far as they can go or too rapidly return the stimulus and incorrectly score this part of the test.  The criteria of no white showing in the corner of the eye must be met.  A nystagmus may be incorrectly mistaken for physiological nystagmus if the officer does not hold the stimulus out to the side for two or three seconds.

In approximately 50% of the suspects they encounter, a physiological nystagmus will be apparent when the eye initially arrives at maximum deviation. This is due to a person not normally following an object all the way to the side with their eyes, but turning their head to view that object. Consequently, a certain degree of uncomfortableness is experienced, causing a slight twitching of the eyes at this location.  If the officer brings the eyes out to the side and then immediately brings them back, he may be scoring this physiological nystagmus inappropriately.  Everyone has a physiological nystagmus, but it is not visible to the naked eye.  The reason it exists is to exercise the eye muscles, lubricate them and prevent atrophy. Remember the jerkiness must be distinct and obvious to be scored a point.

Finally, in regards to the horizontal gaze nystagmus, is the last clue known as angle of onset.  This is the most difficult to evaluate.  If a suspect exhibits this clue in one eye, the probability increases that all the other clues will be seen as well.  This does not work in reverse though.

And that concludes this installment of Standard Field Sobriety Tests.  If you’ve failed a standard field sobriety test and been arrested for DUI because the officer didn’t properly perform the eye examination or due to a preexisting optical condition, call me, defense attorney Leon Matchin, at (833) 732-7320.  There are many reasons that could have caused you not to score well when being reviewed for optical signs of drunkenness.

Next time we will continue with the Proper Administration of the Eye Exam in Part IV of our Standard Field Sobriety Tests series.

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