Cross-Examination on Horizontal Gaze Nystagmus in a Drunk Driving Case

Attorney - Isn't it a fact that the federal guidelines recommend 10 degrees per second on the first movement and 20 degrees per second on the second one?
Officer - Well, that's not how we do it.

Attorney - You disagree with these national standards?
Officer - I do it the way everyone else on the patrol does it.

Attorney - So you believe your own system is more accurate?
Officer - It's accurate, sure.

Attorney - Sergeant, at what angle did you first detect jerking in my client's eyes?
Officer - It was before 45 degrees. 41 degrees, as I recall.

Attorney - What did you do then?
Officer - What did I do? I estimated the angle and determined that he failed the test.

Attorney - (Reading) "When he first detects a slight jerking, he should stop moving the stimulus to make sure that the jerking continues..." That's from the NHTSA manual, Sergeant. I didn't notice you do that in your demonstration.
Officer - When the jerking starts, that's the end of the test.

Attorney - (Reading) "If the nystagmus stops, then the officer has not found the point of onset and he should continue his examination...." Do you recall these instructions from the NHTSA manual?
Officer - Not really.

Attorney - According to the manual, initial jerking of the eyes may be a false sign of nystagmus, right?
Officer - Maybe.

Attorney - According to the manual, you're supposed to stop movement when jerking starts and watch to see if the jerking continues.
Officer - If that's what it says.

Attorney - If you don't stop and wait, if you just end the test, you may get a false point of onset, right?
Officer - Maybe.

Attorney - And a false result—maybe showing a sober person to be intoxicated?
Officer - If you get a false result.

Attorney - You're trained to look for three signs of intoxication in the nystagmus test—angle of onset, smooth pursuit and distinctive jerking, at maximum deviation?
Officer - Correct.

Attorney - And, in fact, the NHTSA manual recommends using all three criteria in the test, right?
Officer - Correct.

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Attorney - So when you conducted the test, you moved the pen to the lateral extremes of my client's eye range?
Officer - I did.

Attorney - Did you note how much white of his eyes was showing at the extremes?
Officer - Whites of his eyes? That has nothing to do with distinctive jerking at the extremes.

Attorney - So you did not take note of the whites of his eyes in this test of yours?
Officer - Of course not.

Attorney - (Reading) "Since some individuals cannot deviate their eyes more than 45 degrees, some white of the eye must show to ascertain that nystagmus is not occurring at the most extreme deviation for that individual."
Officer - That's not how we were trained.

Attorney - In other words, the jerking you saw in my client's eyes could have been because he was at his extreme deviation at 45 degrees—not because he was intoxicated?
Officer - I doubt that, counselor.

Attorney - Well, we don't know, do we? Because you did not check. What was the amplitude of nystagmus at the maximum lateral deviation?
Officer - The what?

Attorney - The degree of eye jerking at the furthest movement of the eye, Sergeant.
Officer - Maximum deviation, yes, there was distinctive jerking at the maximum deviation.

Attorney - But what was the amplitude?
Officer - I didn't really notice.

Attorney - Did you consider "smooth pursuit" as a factor in the nystagmus test?
Officer - I did.

Attorney - And did you consider this an accurate indication of intoxication?
Officer - I did.

Attorney - As accurate as onset?
Officer - Yes.

Attorney - You place a lot of weight on it?
Officer - I suppose so, yes.

Attorney - Then, again, you disagree with NHTSA? (Reading) "Smooth pursuit eye movement... is the least reliable of the three signs."
Officer - My understanding was that all three were equally reliable.

Attorney - Sergeant, what was my client's score on your nystagmus test?
Officer - Score?

Attorney - Yes, what was his total score on the test?
Officer - There's no score, counselor. You either pass or fail. He failed.

Attorney - (Feigning surprise) Then your test is entirely subjective?
Officer - It is based upon my observations.

Attorney - YOU decide whether he passed or failed?
Officer - Of course.

Attorney - Why do you choose not to use an impartial, objective scoring system?
Officer - You can't score a nystagmus test, counselor. Either the jerking indicates intoxication or it doesn't.

Attorney - Are you aware that NHTSA recommends an objective scoring system?
Officer - I am not.

(Attorney has the officer review the report.)

Attorney - Have you now reviewed NHTSA's scoring sheet?
Officer - I have.

Attorney - Apparently, using the objective system, four of six possible points indicates failure, right?
Officer - Apparently.

Attorney - Do you still think it's not possible to use an objective method for deciding whether a person passes or fails the test?
Officer - I suppose it's possible, but it's not how we were trained.

Attorney - Sergeant, you've read the NHTSA law enforcement booklet, Guide for Detecting Drunk Drivers at Night?
Officer - I think that was in the stuff you mailed me.

Attorney - Isn't it true that NHTSA studies indicate that even if nystagmus is administered exactly as recommended, the test has only a 77 per cent reliability factor?
Officer - That's what it says.

Attorney - So, even if the test is done as recommended, you will be right only three out of four times?
Officer - Apparently.

Attorney - Even if you gave the test as recommended, one-fourth of those who "fail" will be... innocent?
Officer - Apparently.

Attorney - And you admit that you did not give the test as recommended?
Officer - I gave it the way I was taught.

Horizontal Gaze Nystagmus
Excellent article summarizing facts/issues on the "HGN" field sobriety test ("follow the pen with your eyes"), from the University of Missouri Law School.

The Science and the Law
A resource guide for judges, prosecutors and law enforcement that deals with Horizontal Gaze Nystagmus.

DUI Arrest FAQs
The 20 questions most frequently asked by those arrested for DUI, from a California lawyer.