DUI Lawyer: What is sobriety eye test?

The Horizontal Gaze Nystagmus, or, HGN, is one of a battery of standardized field sobriety tests, or, SFSTs, used throughout the State of Iowa pursuant to the National Highway Traffic Safety Administration DWI Manual and SFST law enforcement training.

The SFSTs, of which there are typically three + the preliminary breath test (PBT), are typically used to accumulate reasonable grounds to invoke implied consent, temporarily detain a motorist, and place before him or her the hard choice of either consenting to a Datamaster DMT test or refusing same. With the exception of the PBT they may also be used to establish guilty on the issue of intoxication.

HGN field conditions are subject to scrutiny—for example, due to passing, head-lighted cars at night or the use of activated emergency lights. But overall, a test subject’s performance on the HGN is the subjective interpretation of the officer not subject to review on any video recording.

Rather than tell you what my opinion of it is, allow me to quote the NHTSA DWI Manual.

“Horizontal Gaze Nystgamus (HGN) refers to an involuntary jerking occurring as the eyes move side to side.” 2006 NHTSA DWI Manual p. VII-2. The premise is that intoxication “becomes readily noticeable when a person is impaired” and occurs “sooner” as alcohol concentration increases.

The NHTSA believes that this is the “most reliable” of all the tests and notes that nystagmus is both involuntary and imperceptible to the test subject—thus making it more difficult to fake.

Officers look for three things in each eye: smooth pursuit, a “sustained and distinct nystagmus” at “maximum deviation” (as far as the eye can move to the side without moving one’s head does the eye jerk noticeably and repeatedly), and prior to “onset of 45 degrees” does the eye jerk noticeably. Because a test subject has two eyes, there are a total of six points.

The NHTSA in 1977 sponsored a “study” of the effectiveness of this field sobriety test and purportedly found that in 77% of test subjects, those who showed four or more of these “clues,” or, signs of insobriety, were over .10 grams of alcohol per 210 L breath while the other 23% fell below that.

A more recent study from 1998 purports to validate the HGN for BACs between .04 and .08 because of changes in the law that lowered the presumptive level of intoxication throughout the United States from .10 BAC to .08.

Thus, four clues in the HGN is the so-called “decision point” in the HGN.

Critics blast the HGN as pseudoscientific even when performed under laboratory conditions. What makes it worse is that it is a field sobriety test, meaning it is conducted under field conditions, in the dark, with varying and highly contrasting light sources.

Unfortunately, the lack of "science" in this scientific-sounding test is, ironically, what makes it admissible under Iowa law-- as long as the judge agrees the observations are sound and the officer is properly trained within the judge's sound trial court discretion.

In State v. Muphy, the Iowa Supreme Court held that a trained officer's test administration was no different than watching a test subject's performance on the Walk and Turn or One Leg Stand. The Court reasoned:

"The Iowa Law Enforcement Academy and the U.S. Department of Transportation view the horizontal gaze nystagmus test as one of three reliable indicators of intoxication and recommend its use as a field sobriety test. [the test administrator] has been professionally trained to properly administer the test and objectively record the results. The ease with which the test may be administered and evaluated obviates the need for a more scientific interpretation."

State v. Murphy, 451 N.W.2d 154, 158 (Iowa 1990).

The NHTSA loves this case-- and in fact, cites it in both their 2006 and 2013 DWI SFST manuals for all law enforcement agencies throughout the United States to trumpet the scientific acceptance of the HGN. But other Courts, including appellate courts in Illinois, New Jersey, Michigan, and North Carolina, as well as the Fourth Circuit, have all criticized the admission of HGN evidence without a proper scientific foundation.

If you or a loved one has been arrested for OWI (DUI) in the State of Iowa, you owe it to yourself to become an informed legal consumer. Contact David A. Cmelik Law PLC for an initial consultation today.