Something in the back of my mind is tickling at me that there are problems with the scientific validity of HGN when the subject is lying on their back. I looked through most of my materials and couldn't find a definitive answer. Do I remember seeing this somewhere, or am I just recalling some defense B.S.?

Email Clay Abbott, because I remember him saying that most of the assumptions about HGN requirements were false. Basically, I remember him saying that so long as the subject could see the stimulus and the officer could see the eye movement, that it was valid. I am sure that is way over-simplifying, but I definitely remember his example: If the subject is standing on the 50 yard line of a football field and someone is running back and forth with a giant torch (stimulus) on the other 50 yard line, so long as the officer is where he can see their eye movement, then the test is valid. I know that is primarily concerned with distance between the subject and the stimulus, and not head orientation, but I seem to remember this being just one part of a long segment about how the test works in many circumstances that don't fit the standard testing procedures.

If I remember correctly, it has to do with PAN having an effect. According to some Web sources, the 2002 NHTSA Instructor Manual indicates not to perform HGN on a subject lying down (pg. VIII-7). I can't get ahold of this text anywhere. Does anyone have a copy for reference?

I think there is only one 50 yard-line on a football field but there are two of every other yard-line.

I am not a lawyer but am a police officer and was assigned to a DWI Task Force as an officer and a supervisor for 6+ years. Dr. Karl Citek, who is one of the leading authorities on HGN, published an article on HGN and its reliability in various positions, including supine. The results of his study validate HGN in the supine position and from my understanding this information will be published in future SFST's manuals, but the government moves slow in making changes. If you need further information, please feel free to contact me. The following link will take you to the published study:

www.ndaa-apri.org/pdf/nystagmus_testing.pdf