The Horizontal Gaze System (HGN) is the third nationally standardized field sobriety test.
In this test, the officer monitors the defendant’s eyes, which are following a moving object, usually the tip of a pen.
The pen is approximately six inches from the defendant’s nose, and slowly move each shoulder and then toward the forehead and chest. If the eye begins jerking, as opposed to a smooth pursuit, before the pen reaches a 45-degree angle, this represents alcohol impairment.
Accuracy – Of all the sobriety tests, the HGN is most accurate, though it is only 77% reliable. In other words 23 out of 100 individuals would fail the test despite being sober.
Laboratory Conditions – Although the HGN measures an involuntary physical response, it still has serious flaws. The test’s accuracy is a product of ideal laboratory conditions—adequate lighting and precise measuring devices.
In most drunk driving arrests, the test is performed on a dark street with officers using streetlights, headlights, or a flashlight for illumination, and no instruments are available to measure a 45-degree angle. It is extremely difficult to monitor a jerking of the eye, and the test result is wholly unreliable at a 55-degree angle.
There’s no substitute for a strong Sacramento DUI lawyer,
call Wing & Parisi at (916) 441-4888.
Law Office of Wing & Parisi
Sacramento DUI & Criminal Defense Attorneys
917 G Street
Sacramento, CA 95814, USA
March 15, 2015
The Law Office of Wing & Parisi serves clients in the Sacramento and Davis communities as well as throughout
Placer County and San Joaquin County. Hablamos espanol.