A great point was made recently by Jamie Spencer (through George Scharmen at the Rusty Duncan Criminal Defense Seminar put on by TCDLA) regarding the cross examination of an officer about HGN.
Jamie points out in "Nystagmus, Mostly Leave it Alone" that not a lot of cross examination is necessary. Mark Bennett agrees in his comment that "juries are duly unimpressed with the ‘pen voodoo’ as one juror called it post-trial."
Here is my take on it:
I almost never spend a lot of time on the issue. Spending a lot of time just makes it seem like you care about it. I feel that a trial is about whatever you decide it is about. If I spend an hour talking about how many passes it takes for the Lack of Smooth Pursuit, it only shows how worried I am about that testimony.
This especially holds true on a refusal case. In a refusal case (no breath test, and no vampire blood draw), the only issue is if the citizen accused lost the normal use of their mental or physical faculties.
Question 1. If someone has HGN, do they even know it is there? — Officer answer, "No"
Question 2. Does HGN affect the vision? — Officer answer, "No"
Statement to the jury — Well then, who the heck cares? It doesn’t affect your faculties! So what difference does it make?
I have found that most juries could care less about the HGN test, and the testimony that follows from it. Conversely, though, almost every offcer I have spoken with feels like it is the most important indicator of intoxication. Go figure.