The Eyes Do Sometimes Lie

The Horizontal Gaze Nystagmus Test: what it is and why it fails

The Horizontal Gaze Nystagmus test, or HGN test for short, has been used by police officers as a roadside test for intoxication for decades. Research began on the subject in 1975 when the National Highway Traffic Safety Administration (NHTSA) teamed up with the Southern California Research Institute (SCRI) and funded a series of studies to find reliable means of identifying impaired drivers.1 


At the time, there were a number of roadside tests used by police departments all over the country.2 The original objectives of this research was to (1) evaluate the different tests then in use and determine their relationship to intoxication and impaired driving; (2) develop more sensitive tests that would provide more reliable evidence of intoxication; and (3) to standardize the more reliable tests for effective roadside administration.3 


1)   DWI Detection and Standardized Field Sobriety Testing; Participant Manual (2018), Session 8, pg 5-6

2)   Id.

3)   Id. at Session 8, pg 6