Several medical specialties use a form of nystagmus testing in diagnosing patients, for example, emergency room physicians, ophthamologists, neuro-ophthamologists. Although not necessary, the testimony of a medical expert supports the use of the HGN test in the broader community, not just law enforcement, and gives the weight of medicine to the validity of the test. It is preferable to use an expert with an interest in the subject beyond just testifying as an expert and who has actually witnessed officers administering the test.

NOTE: The following examination is intended only as a sample. It is adaptable to any medical expert you intend to call. Be sure to discuss the questions in advance with your expert to determine his ability to answer all questions. Delete those which are not appropriate for your expert. Depending on your expert's experience and training, there are many more questions you could ask to qualify the witness as a expert. Do not diminish your expert's credibility by underplaying the qualifications.

1. Please state your name for the record.

2. What is your occupation?

3. Where did you attend college?

4. What did you study?

5. Where did you go to medical school?

6. When did you graduate?

(If the witness received any special recognition in medical school, e.g. valedictorian, be sure to ask about it.)

7. What is your area of practice?

8. Is emergency room medicine a specialty?

9. Is there a board certification for ER medicine?

10. Are you board certified?

11. How long have you been an ER doctor?

12. Where are you currently employed?

13. How long have you been employed at ?

14. Please describe what you do as an emergency room doctor?

15. As an ER doctor, are you required to be familiar with symptoms associated with other medical specialties?

16. Why is that?

17. Do you see many patients who are under the influence of alcohol or other drugs?

18. Approximately how many patients a week do you see that are under the influence of alcohol or other drugs?

(If you have not already done so, this would be an appropriate time to move the court to recognize the witness as an expert. If the witness has testified in court previously about HGN, be sure to ask when, how often, what courts, and whether the witness was qualified as an expert?)

19. What are the symptoms of alcohol impairment?

20. Are you familiar with the term "horizontal gaze nystagmus"?

21. When did you first become aware of HGN?

22. Is HGN a valid medical phenomenon?

23. Please explain what horizontal gaze nystagmus is.

24. Do doctors test for the presence of HGN?

25. How long has HGN testing been in use in the medical community?

26. Do you ever test for the presence of HGN in the emergency room?

27. How often?

28. How do you test for it?

29. Is HGN difficult to identify?

30. What is your purpose in looking for HGN?

31. Are you trained in the effects of alcohol and/or other drugs on the central nervous system?

32. What effect does alcohol have on the presence of HGN?

33. Is it necessary to be a doctor or have medical training to identify HGN?

34. Can non-medical people be trained to identify HGN?

35. Have you ever trained anyone to detect HGN?

36. About how long did it take?

37. Can police officers be trained to test for HGN?

(Ideally your witness is familiar with the HGN test administered by police through personal observation. If not, be sure that he has had adequate time before the hearing or trial to review the NHTSA training manuals on the standardized procedures for the administration of the HGN test.)

38. Are you familiar with the procedures used by police officers to detect HGN?

39. Have you had the opportunity to review the material in this manual related to the administration and interpretation of the HGN test?

(Show the witness a copy of the police officer training manual in use in your jurisdiction.)

40. Have you specifically reviewed page ___ through ___ which specifically refer to the HGN testing and interpretation procedure?

41. Is the procedure used by the police a reliable method of testing for the presence of horizontal gaze nystagmus?

42. Is there adequate time in the training for the officer to learn to administer and interpret the test results?

43. Is HGN voluntary?

44. Can a chronic user of alcohol suppress or control the symptoms of nystagmus?

45. Have you seen a police officer administer the HGN test at roadside?

(Only ask this question if the witness has actually seen police officers administer to the test under field conditions to impaired drivers or in a controlled setting such as a DRE evaluation or alcohol workshop.)

46. Do you have an opinion about the ability of a police officer to administer the HGN test?

47. Upon what is that opinion based?

48. What is that opinion?

49. Do you have an opinion about the ability of a police officer to interpret the test results?

50. Upon what do you base your opinion?

51. What is that opinion?

52. Are there other causes of nystagmus?

53. What are some of these causes?

54. Do you see these causes in the emergency room?

55. Are these other causes more or less common than alcohol induced nystagmus?

56. Referring specifically to other causes of nystagmus, does the nystagmus (bouncing of the eyes) appear the same as alcohol caused nystagmus?

57. Do you know the rate of occurrence of nystagmus in the general population of the various pathologic causes of nystagmus that you have just mentioned?

58. How difficult is it to tell the difference between alcohol caused nystagmus and some of the other causes that you have mentioned?

59. Is a police officer who has been trained in the administration of the HGN test using the NHTSA scoring procedure, looking for 6 clues (3 in each eye), likely to mistake alcohol induced nystagmus for other types of nystagmus?

60. Does caffeine cause nystagmus?

61. Does nicotine?

62. Does fatigue?

63. What is the most common cause of horizontal gaze nystagmus?

64. You testified previously about some of the common symptoms of alcohol impairment?

65. What functions of the body does alcohol affect?

66. Can a chronic user of alcohol develop a tolerance to alcohol?

67. Can he learn to compensate for some of the behaviors associated with impairment, such as poor balance?

68. In your opinion, which is a more reliable indicator of alcohol impairment, the presence of HGN or some of the other commonly associated signs such as slurred speech? poor balance? lack of coordination?

69. Why?

70. Would HGN be visible after one drink?

71. By the time HGN is visible, what effect would there be on the suspect's judgment? ability to process information? coordination?

72. Do you have an opinion about the HGN test as a reliable indicator of alcohol impairment?

73. Upon what is that opinion based?

74. What is your opinion?