Validity of Field Sobriety Test Questioned

Posted by Lawrence Taylor on November 19th, 2007

There are many so-called “field sobriety tests” used by officers supposedly to determine a DUI suspect’s sobriety.  And, as I’ve posted in the past (Field Sobriety Tests: Designed for Failure?), these tests are highly unreliable and largely used to justify the officer’s suspicions.  Of the many “tests” used today, only three have been approved by the National Highway Traffic Safety Administration: walk-and-turn, one-leg-stand and horizontal gaze nystagmus (HGN, or the “eye test”).  Collectively, they are referred to as the Standardized Field Sobriety Tests (SFSTs).  Although they are in reality no more valid at determining intoxication than the other tests, their adoption by the federal government has given them an aura of credibility.  The most insidious of these three tests is the nystagmus test – because of its seemingly scientific nature.  Yet, as I’ve previously posted, HGN is unquestionably the least reliable  of the FSTs. (DUI “Eye Test” a Fraud?).  

 A growing number of states are now questioning the validity of such tests, as shown in the following recent news story:


DUI ‘Eye Test’ Under Fire by Supreme Court

State justices join critics, but test has its supporters, too

When it comes to a suspected DUI, the eyes don’t lie.

That’s the principle behind horizontal gaze nystagmus testing, which has long been considered the most reliable way, short of a blood or breath test, for a police officer to determine whether a driver has been drinking.

However, the Illinois Supreme Court has dealt a potentially serious blow to HGN testing with a recent decision stating that such tests are not presumed scientifically valid in Illinois…

“Based on my training and experience, the test is very reliable,” (Dixon Police Department Sgt. Dan) Langloss said. “Yes, the test does have its flaws and drawbacks, but it is only one factor that we look at during a DUI stop. You have to look at the totality of circumstances.”

Many critics across the country, including defense attorneys, argue it is difficult to determine the accuracy of HGN testing and that there are many factors that can cause the eyes to visibly jerk aside from alcohol consumption.

“There are over 25 different types of nystagmus,” said Bob Thompson, Lee County public defender. “Officers are not taught about the other types, which they should know about. Fear, anxiety and viral infections, to name a few, can all have an affect on the eyes.”

Thompson added there are other factors that can affect the results of an HGN test, such as exposure to the lights on the squad car and the difficulty that an officer may have when determining an exact 45-degree angle when conducting the test.

“Officers are not trained in scientific methods or medicine,” Thompson said. “During cross examination, it’s difficult to ask them to draw us a 45-degree angle or test their geometry skills. That’s where we’re starting to see the trial courts become more strict when admitting the test.”

The court ruling came in the wake of a Peoria County case involving Joanne McKown, who was convicted of multiple counts of DUI and reckless driving after she hit three motorcyclists in June 2002. Having suffered a broken toe, she could not perform other sobriety tests, such as standing on one leg or walking heel-to-toe. A sheriff’s deputy who administered an HGN test 90 minutes after the accident said she failed. After McKown refused to give blood voluntarily, police got a search warrant and drew blood 6 1/2 hours after the accident. Tests showed no alcohol in her bloodstream.

Writing that “HGN testing appears to have as many critics as it does champions,” the state Supreme Court sent the Peoria case back to the trial court in September.


For a further discussion of the pseudo-scientific nystagmus test, see my earlier posts: Nystagmus: ”The Eye Test”, Nystagmus: ”The Eye Test” (part 2) and Nystagmus: ”The Eye Test (part 3)”.


(Thanks to John Kruzelock.)

PinterestRedditDiggShare