The Horizontal Gaze Nystagmus (NHN) test is considered to be the best of the three Standardized Field Sobriety Tests (SFSTs) for apprehending drivers with a
blood alcohol concentration (BAC) of 0.08% or greater. HGN is an involuntary jerking of the eyes that is not controlled by the subject.
Signs of HGN in a suspect's eyes:
- Lack of smooth pursuit (the eye cannot track a moving object at a constant speed);
- Nystagmus at maximum deviation; and
- Onset of gaze nystagmus before reaching 45 degrees.
At the lower levels of impairment, the suspect may only display lack of smooth pursuit, but at the higher levels of intoxication, all three will be present.
Is the HGN test admissible in court?
While the HGN test is admissible in many courtrooms across the nation, some states require a foundation to be laid by the prosecutor. Unlike staggering or slurred speech, visible nystagmus is not something that most judges and jurors have ever observed personally.
In Kansas, Horizontal Gaze Nystagmus (HGN) test results are not admissible at trial without meeting the foundation requirements of Frye for scientific evidence. In Missouri, an officer must have had eight hours training with respect to administering the HGN.
When the court applies the Frye standard (Frye v. United States, 293.F. 1013), it means the court must determine whether or not the evidence obtained was generally accepted by experts in the field of which it belongs.
Challenging the HGN Test
The HGN test poses the most problems out of the SFSTs because the defendant cannot see their own eyes and they have no idea of they passed or not. A video will not show the defendant's eyes, so the jury cannot make an independent evaluation.
The testifying officer must demonstrate his or her expertise and training in the area of administering HGN tests. Many officers are poorly trained in administering HGN test.
If there is a video of the stop, it's easier to challenge the HGN because a skilled DUI defense attorney can observe how the officer administered the test, and determine if it was administered correctly.
Arrested for DUI? Contact Kansas City DUI Attorney Steve Schanker. With 25+ Years of experience, he can provide you with excellent DUI defense representation – call today!