612.2Horizontal Gaze Nystagmus (“HGN”)

Suggested Questions
Last Updated: 12/01/23


Practice Pointer

Other witnesses, other questions 
For an alternative set of HGN questions to use with the officer who administered the test, or suggested questions to use with other types of HGN witnesses such as researchers, paramedics, etc., see the Appendices of this Resource Guide for DWI prosecutors.  

Suggested Questions for Qualifying the Witness: 

[Even though Rule 702(a1) and State v. Younts, 254 N.C. App. 581 (2017) make HGN testimony admissible without further proof of reliability, the witness still must be qualified as an expert in HGN before the testimony is allowed.] 

1.  Officer, let’s talk about the field sobriety tests you administered in this case – in particular, I want to ask you about a test known as horizontal gaze nystagmus, or HGN? Are you familiar with this test? 

2.  Can you (very briefly) describe what the HGN test is? 

3.  Have you received any specific training in administering the HGN test?

4.  Where did you receive this training? 

5.  How many hours of training did you receive? 

6.  Generally, what did this training cover? 

7.  Who were your instructors?  

8.  Was there an “alcohol workshop” or “controlled drinking” exercise as part of this training? 

9.  Who were the subjects at this workshop/exercise? 

10.  Do all the subjects at the workshop/exercise drink? How much do they drink? 

11.  Did you administer the HGN test to the subjects in that workshop/exercise? 

12.  What did you observe in those subjects? 

13.  Other than at the workshops/exercise, have you ever administered the HGN test to persons who you knew were not impaired? 

14.  Under what circumstances? 

15.  What differences have you observed in the eye movements of sober persons vs. impaired persons in doing this exercise? 

16.  As part of your training in HGN, were you required to pass any kind of skills evaluation or examination? 

17.  Please describe that examination or evaluation process. 

18.  As a result of your training, did you receive a certificate? 

19.  What organization issued you that certificate? 

20.  Do you have the certificate here with you today? 

[If so, may admit the certificate (or a copy) into evidence.] 

21.  Have you had any additional or follow-up training in the administration of HGN, other than what you’ve already described? 

22.  If so, please describe that additional training? 

23.  Approximately how many times would you say you have administered the HGN test? 

[Do you keep a log or record of this? Why or why not?] 

24.  Have you ever previously been qualified as an expert in administering the HGN test? 

[If so, how many times, and in which courts?] 

Tender the officer as an expert in administering the HGN test. 

Suggested Questions for Results of HGN Test: 

[Although the state is not required to establish the reliability of the test itself, it still must show that the witness applied the principles and methods reliably in this case, per Rule 702(a)(3).] 

1.  Is there a standard way in which the HGN test should be given? 

2.  Please describe how that test is done. 

[Check pupil size, equal tracking, hold stimulus/stylus up, move to the side, hold for certain amount of time, and so on.] 

3.  What specifically are you looking for when you give this test? 

[Looking for 6 clues.” This means three indicators: (i) lack of smooth pursuit, (ii) distinct and sustained nystagmus at maximum deviation, and (iii) angle of onset prior to 45 degrees, and checking both eyes = total of six clues] 

4.  Did you give the test to the defendant in this case in the way you just described? 

5.  Did you ask the defendant if he/she understood what he/she was supposed to do? 

6.  Did the defendant indicate that he/she understood? 

7.  Did the defendant have any difficulty in following your instructions? 

8.  Let’s talk about those “six clues” you mentioned earlier, starting with the first one, “lack of smooth pursuit” – please describe what that term means? 

9.  When you gave this first part of the test to the defendant, what did you see? 

10.  What about the second part of the test, “distinct and sustained nystagmus at maximum deviation” – please explain what that means? 

11.  How long do you hold the stylus at the point of maximum deviation? 

12.  Why? 

13.  When you gave this second part of the test to the defendant, what did you see? 

14.  Now the third part of the test, “angle of onset prior to 45 degrees” – please explain what that means? 

15.  How is this part of the test done? 

16.  How do you estimate the angle of onset? 

17.  When you gave this third part of the test to the defendant, what did you see? 

Suggested Questions for Opinion and Conclusions: 

1.  So in total, how many clues did you observe when you performed the HGN test on the defendant? 

2.  Based on your training and experience, what does the presence of [two, four, six] clues on the HGN test indicate? 

3.  In your experience, is there a connection between HGN and the amount of alcohol a person has consumed? 


4.  What is that connection? 

[The witness is not permitted to opine as to a specific BAC level based on angle of onset, but the witness should be permitted to testify that (a) people who have been drinking tend to show nystagmus, and (b) the more they have had to drink, the easier the nystagmus is to see. The judge may even allow the witness to say that “the earlier the angle of onset, the higher the BAC tends to be,” but the witness should avoid offering any testimony regarding a direct numerical correlation.] 

5.  In this case, did you conclude that the clues you observed when you administered the test to the defendant were an indication of impairment? 

6.  Overall, based on all the training and experience you previously described, what did your observations of the defendant’s performance on the HGN test indicate to you?