Despite its history of use and the endorsement of the Department of Transportation's National Highway Traffic Safety Administration, the horizontal gaze nystagmus (HGN) field sobriety test is not fully understood. What is nystagmus? How does the presence of horizontal gaze nystagmus reflect alcohol impairment? How does the police officer test for HGN? What conclusions can reasonably be drawn from the presence of HGN? In an effort to provide accurate information regarding the use of the HGN test in impaired driving enforcement and dispel the continuing controversy around HGN, the American Prosecutors Research Institute (APRI) is pleased to provide criminal justice practitioners nationwide with this document. Among other things, this guide provides an overview of the science supporting the HGN test as a valid indicator of impairment, distinguishes between HGN and other forms of nystagmus, and provides the necessary tools to establish admissibility of the HGN in court. (Author/publisher)
Abstract