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

Attorney - Sergeant, assume in a given case that you've got an angle of onset before 45 degrees.
Officer - Okay.

Attorney - What does that tell you?
Officer - The subject is probably under the influence of alcohol.

Attorney - Where does the 45 degrees figure come from?
Officer - I don't know.

Attorney - Please feel free to refer to the manual at any time, Sergeant, but aren't there two reasons?
Officer - That sounds familiar.

Attorney - Isn't the first reason that 45 degrees is close to the angle of onset for a person with a .10 percent blood-alcohol concentration?
Officer - Again, that sounds familiar.

Attorney - And what is the second reason for using the nystagmus field sobriety test to determine intoxication?
Officer - I don't recall.

Attorney - (Reading from manual) "...and because it is easy to estimate." Is that correct, Sergeant?
Officer - That's what it says.

Attorney - You mean, nystagmus is used to test for intoxication because it's only close—to how an average person's eyes will react?
Officer - Apparently.

Attorney - And because it's easy for the police?
Officer - Apparently.

Attorney - Sergeant, does the report indicate a third reason for using nystagmus?
Officer - A third reason?

Attorney - Does it say the test should be used because it's accurate?
Officer - Apparently not.

Attorney - Sergeant, do you consider nystagmus an accurate test of intoxication?
Officer - I think it's fairly accurate, yes.

Attorney - But the state of Kansas has not approved it as a blood-alcohol test,have they?
Officer - A blood-alcohol test? No.

Attorney - You've read an article concerning a study of the accuracy of nystagmus, reported in 25 Journal of the Forensic Society 476 (1985)?
Officer - I believe that's one of the things you mailed me.

Attorney - The study was conducted by a law enforcement agency—the Santa Clara County Criminalistics Laboratory, in Ohio?
Officer - I believe so.

Attorney - They analyzed 129 actual cases where nystagmus was given—and compared them with actual BACs, right?
Officer - I believe so.

Attorney - What were the results of that study?
Officer - I believe there was some discrepancy.

Attorney - The officers consistently erred in estimating BAC, correct?
Officer - There was some error.

Attorney - What was the conclusion reached by these researchers, Sergeant?
Officer - They felt there were potential problems with nystagmus.

Attorney - In fact, didn't they conclude that nystagmus cannot be used to predict accurately the blood-alcohol level of a suspect?
Officer - Something like that, yes.

Attorney - You've read ''Psychophysical Tests for DUI Arrest'' by Tharp, a study commissioned by NHTSA?
Officer - Again, counselor, I believe you mailed it to me.

Attorney - Well, didn't that study conclude that some individuals with no alcohol in their systems demonstrated early onset of nystagmus?
Officer - I believe so.

Attorney - In other words, the nystagmus test showed perfectly sober people to be intoxicated?
Officer - Apparently it can happen in isolated instances.

Administration of Test
(Note: The officer demonstrate exactly how he administered the nystagmus test to the client in field.)

Attorney - In the demonstration you just gave, I notice that you didn't ask my client if he was wearing contact lenses?
Officer - It must have slipped my mind.