DUI Defense – Attacking a horizontal gaze nystagmus test: the way the test was given

Last Modified: June 18, 2024

DUI Defense – Attacking a horizontal gaze nystagmus test: the way the test was given

The horizontal gaze nystagmus test must be given correctly

The first goal in the attack on a horizontal gaze nystagmus test (HGN) is to assess if it was properly administered. There are at least 25 different steps that need to be performed to properly conduct the HGN test. These procedures must be followed with precision and failure to do so renders the results unreliable.

Even if the officer administered the HGN test flawlessly, the test is still subject to attack. For example, in cross-examination of the arresting officer your attorney might point out that HGN can be caused by a number of reasons other than alcohol intoxication, that HGN occurs naturally in some people, and that fatigue, illness, hypertension, and common drugs like caffeine or aspirin may contribute to HGN.

Sample cross-examination of arresting DUI officer about the horizontal gaze nystagmus test

The following is a sample cross-examination of an officer by Criminal Attorney Rabin Nabizadeh in a DUI trial in Oakland California :

Q: Officer which direction was [the defendant] facing when you looked at her for horizontal gaze nystagmus?
A: I think she was facing north, but I am not exactly sure.
[If the officer is not sure which way the defendant was facing the officer cannot tell if the defendant was facing the lights of oncoming traffic.]

Q: You told the defendant to put her feet together?
A: Yes.

Q: You told her to place her hands at her side?
A: Correct.

Q: And she did as you asked?
A: She did.

Q: She was cooperative with you?
A: Yes she was.

Q: You told her to keep her head still?
A: Yes.

Q: And she did keep her head still?
A: Yes, her head was still.

Q: Officer as you eyeballed the defendant’s eyes how far away were you?
A: I was probably two feet away.

Q: When you were peering into the defendant’s eyes did you wave a pencil or wand back and forth in front of her eyes?
A: I moved a pencil.

Q: Which way did you go first?
A: I went toward her left eye.

Q: How far away did you hold the pencil?
A: About 8 to 10 inches.
[This is an incorrect answer. The stimulus should be held 12 to 15 inches away.]

Q: That is not the proper distance is it?
A: It is about where I usually place it.

Q: How long did it take you to move to the side of the defendant’s left eye?
A: I do not really keep track, probably a couple of seconds.

Q: How many passes did you make?
A: I do one pass to each eye.
[This is an incorrect answer. The proper procedure is two times for each eye.]

Q: You said you observed the onset of nystagmus prior to 45 degrees?
A: Correct.

Q: Did you do that at the same time you were checking for smooth pursuit?
A: I did.
[This is an incorrect answer. Checking for lack of smooth pursuit should be done separately in a different stage of the test.]

Q: Nystagmus occurs naturally in people?
A: In some people.

Q: Disease causes it as well?
A: It can.

Q: Well, Wernicke’s encephalopathy causes it, doesn’t it?
A: I am not sure.

Q: Do you know if influenza can cause nystagmus?
A: I am not sure.

Q: Well how about hypertension, vertigo, arteriosclerosis or even sunstroke, can’t they also cause it?
A: Again, I do not know about diseases.

Q: Well how about non-diseases. The consumption of caffeine can cause nystagmus?
A: That I have heard.

Q: Aspirin?
A: I do not know.

Q: What about nicotine? Doesn’t that cause nystagmus?
A: I am not sure.

Q: Well do you know if my client had a cigarette before you stopped her?
A: I do not.

Q: Do you know if she was around other people who were smoking?
A: I do not know.

Q: Do you know if she had any coffee earlier?
A: I did not ask her.

Q: Did you ask her if she had consumed any soft drink beverages that contained caffeine in them, like diet Coke or Pepsi?
A: No.

Q: Eyestrain will cause nystagmus too?
A: Yes.

Q: Eye muscle fatigue will also present itself as nystagmus?
A: It can.

Q: Prior to you arresting her, do you know if the defendant was doing any work that could create eyestrain, for example working at a computer?
A: I do not know.

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