Attacking a horizontal gaze nystagmus test: the officer’s qualification to conduct the test

The horizontal gaze nystagmus test is an ophthalmologic examination

The horizontal gaze nystagmus test is a test of a person’s eye movements. With one eye closed the individual fixes the other eye upon a pencil-beam of light from a pocket flashlight held by the officer. When the officer moves the beam from left to right and vice-versa, a jerking movement of the eye as it follows the beam of light will occur when the light beam has reached a deviation of 40° or more. Alcohol is said to cause these deviations at lesser angles.

The horizontal gaze test is an opthalmologic examination that requires substantial experience in recognition of the aberration itself (that is, the degree at which the deviation occurs). Many potential eye and neural disorders, and many drugs, can affect the test results.

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

The following is a sample cross-examination of an officer about the horizontal gaze nystagmus test used by a Summit defense attorney in a DUI trial in San Jose:

Q: Officer, you have received training in the horizontal gaze nystagmus test, correct?
A: Yes.

Q: The HGN test is really an ophthalmological examination, correct?
A: Yes.

Q: You are not an ophthalmologist, are you, officer?
A: No.

Q: You have had no specified training in ophthalmology, have you, officer?
A: No.

Q: You have not taken any courses in ophthalmology, have you, officer?
A: No.

Q: You hold no degree in ophthalmology, do you, officer?
A: No.

Q: As part of your training in HGN, were you informed that there are many potential eye disorders that can affect the test results?
A: Yes.

Q: You are not qualified to determine whether Mr. Jones had, or has, any eye disorders, are you?
A: No.

Q: In fact you do not know whether he had or has any eye disorders, do you?
A: No.

Q: Yet eye disorders would affect the HGN result, correct?
A: I believe so.

Q: Were you also taught in your course in HGN that neural disorders can also affect the HGN test result?
A: Yes.

Q: You have no special training in detection of neural disorders, do you officer?
A: No.

Q: You did not perform any tests to determine whether Jones suffered from any neural disorders, did you?
A: No.

Q: You did not consult any medical records of Mr. Jones to determine whether he had any neural disorders, did you?
A: No.

Q: You did not ask Mr. Jones whether he suffered from any neural disorders, did you?
A: No.

Q: Officer, you were also informed that many prescription drugs can affect the HGN test results, correct?
A: Yes.

Q: When you stopped Mr. Jones and placed him under arrest, you conducted a physical inventory of his personal property, did you not?
A: Yes.

Q: In that physical inventory, one of the things that you found was blood pressure medication, correct?
A: Yes.

Q: You verified that prescription, did you not?
A: Yes.

Q: Mr. Jones properly had a prescription for blood pressure medication, correct?
A: Yes.

Q: The blood pressure medication can affect nystagmus, correct?
A: I do not know.

Q: Did you consult any sources at the time you administered the HGN test to determine whether in fact the blood pressure medication taken by Mr. Jones might affect the test result?
A: No.

Q: You assumed it would not, correct?
A: Yes, I assumed it would not.

Q: Yet in your course you were told that certain prescription drugs can affect the test results, correct?
A: Yes.

Q: And you don’t recall what specific prescription drugs can affect the test results?
A: Not specifically, no.

Q: In fact, you don’t recall how prescription drugs may affect the test results, do you?
A: No.

This line of questioning has demonstrated that there are many other causes of nystagmus other than alcohol intoxication, and that the officer is not an expert in the science behind the test.