Final answer:
The Arizona State Supreme Court case that established the admissibility of HGN as evidence of alcohol impairment was State V. Blake.
Step-by-step explanation:
The landmark Arizona State Supreme Court case that established admissibility of Horizontal Gaze Nystagmus (HGN) as evidence of alcohol impairment was State V. Blake. This case is significant because it set a precedent for using HGN test results as a reliable indicator of intoxication in DUI cases. The HGN test, an element of field sobriety tests conducted by police officers, can be used to infer a driver's level of impairment due to alcohol consumption. The use of HGN as evidence helps in bringing scientific methods into court to support the accusation of impaired driving and demonstrates the ongoing evolution of legal standards on the admissibility of forensic evidence in trials.