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DUI Field Sobriety Tests – The “Eye Test” and its Limitations

DUI Eye Test - Limitations - Seattle Criminal Lawyer Blog

There are three standardized tests all officers in Washington are trained to administer during DUI Detection.

When I was in my early twenties, my best friend drove me to a New Year’s Eve party. He was the designated driver for the night. He drank one beer. The night was long. After the music stopped I hopped into my friend’s car and we began to head home. As we drove down a long county road my friend was pulled over by a deputy sheriff.

I recall the sheriff approaching the car and asking my friend for his license and registration. All documents were produced without issue. The sheriff then asked him how much he had to drink. My friend was honest and replied, “I had one beer a long time ago.” The officer asked him to step out of the car. That is when I saw him checking his eyes. The eye test took a little bit, but eventually the officer let my friend go on his way (unusual these days).

I recall my buddy coming back into the car saying something along the lines of “I didn’t have any problem with that test. It wasn’t hard to follow his finger.”


The test is called the “horizontal nystagmus test” or “HGN.” Nystagmus is the involuntary jerking of the eye. The test is not intended to determine whether the driver can follow the stimulus (i.e. pen or pen light in most cases) as my friend thought. The officer looks for the involuntary jerking of the eye. This involuntary jerking can become evident after a person has consumed alcohol.

That is, positional alcohol nystagmus (PAN) occurs when a foreign fluid, such as alcohol, alters the specific gravity of the blood in unequal concentrations in the blood and the vestibular system and causes it to respond to gravity in certain head positions–resulting in nystagmus.

Officers are trained to look for a total of six clues in the eye test (three in each eye):

  1. Lack of smooth pursuit
  2. Distinct and sustained nystagmus at maximum deviation
  3. Onset of nystagmus prior to 45 degrees

Lack of smooth pursuit exists where the eye jerks noticeably as it moves side to side. Distinct and sustained nystagmus is present when the eye is moved as far to the side as possible and is kept at that position for four seconds and jerks distinctly in that position.

Onset of nystagmus prior to 45 degrees occurs when the eye begins jerking prior to a 45 degree angle as it moves toward the side. The National Highway Traffic Administration claims its research shows that four or more clues has a correlation with a .10 blood alcohol concentration or more and that the test is accurate 77% of the time.

However, this research has not been peer reviewed.

In State v. Baity, the Washington Supreme Court analyzed HGN testing in the context of Drug Recognition Expert (DRE) protocol. It held that HGN testing is scientific in nature and is generally accepted in the relevant scientific communities (thereby passing the Frye test–a standard that must be passed for scientific evidence to be admissible).

However, the court placed limitations on the use of such evidence. The court stated “an officer may not testify in a fashion that cases an aura of scientific certainty…” The court also emphasized, “The officer also may not predict the specific level of drugs present in a suspect. The DRE officer, properly qualified, may express an opinion that a suspect’s behavior and physical attributes are or are not consistent with the behavior and physical signs associated with certain categories of drugs.”

More recently, in State v. Quaale, the Supreme court revisited HGN evidence in the context of DUI allegations involving alcohol. The court confirmed the limitations on HGN testing set forth in Baity apply equally in DUI investigations involving alcohol.

It further confirmed that the officer cannot testify in a fashion that casts an aura of scientific certainty and may not predict a specific legal of alcohol. The officer may only express an opinion whether the suspect’s behavior and physical attributes are or are not consistent with signs of alcohol consumption.

This means that the officer cannot claim a driver is “impaired” based on HGN testimony or claim there is “no doubt” the driver is “impaired.”

In Quaale, a driver was supposedly speeding at 56mph in a 25mph. The cop activated his lights to try to pull the driver over, but the driver allegedly turned off his headlights and accelerated. Eventually, the driver lost control, overshot a corner, and skid into someone’s yard – but the driver then regained control of his truck and continued to flee for several more blocks until finally pulling over.

The officer smelled an odor of alcoholic beverages on the driver’s breath and then performed an HGN test on the driver. No other field sobriety tests were performed. The driver was arrested and refused a breath test after receiving implied consent warnings at the station.

At Quaale’s trial the trooper testified “there was no doubt he was impaired.” Quaale was convicted of DUI. But the Washington Supreme Court reversed the conviction and remanded the case for a new trial.

The Supreme Court reasoned that the HGH test “…cannot establish impairment by itself, and testimony to the contrary violates the limitations imposed by our decision in Baity.”

Contact an attorney if you have questions about how standardized field sobriety testing was used in your case and how such evidence may be limited or undermined.