Involuntary Field Sobriety Tests

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.

Contact us online or call at (916) 441-4888 for a free and confidential initial consultation, available in Spanish. We appear in state and federal courts in the Sacramento and Davis communities as well as throughout Placer and San Joaquin counties.
Linda Parisi
Law Office of Wing & Parisi
Sacramento DUI & Criminal Defense Attorneys
917 G Street
Sacramento, CA 95814, USA
(916) 441-4888
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.