HGN and “Lazy Eye”

Lazy eye, or Amblyopia, is a condition which, in my opinion, invalidates the Horizontal Gaze Nystagmus (HGN) test of the standardized field sobriety tests (SFSTs) described in the NHTSA manual. The 2004 NHTSA DWI Detection and Standardized Field Sobriety Testing, Student Manual, directs law enforcement officers to ask about medical conditions.

One would think that if a person answered yes and had a condition like a “lazy eye” that would be the end of it; instead, the manual (Section VIII p.8) seems to just instruct the police officer to proceed with the test and just note the medical condition. Law enforcement officers rarely deviate from their testing procedures because they don’t really know what else to do and because that is how they have been trained. They will report their findings even though they are completely invalid.