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.
"This could mean that there will be a change in the law when it comes to prosecuting DUI cases," said Lee County State's Attorney Paul Whitcombe.
Sgt. Dan Langloss of the Dixon Police Department said the test is simple if performed the right way. The officer will use a pen and place it approximately 6 inches away from the person's face and have the person track the movement from side to side.
The officer checks for three things: whether the person's eyes are unable to follow the pen smoothly without visible jerking; when moving each eye as far to the sides as possible and holding for five seconds, the eye jerks more noticeably; and the eye begins to jerk before moving 45 degrees to the side.
Langloss said if the officer observes these and other clues in both eyes during the test, it is likely that the person's blood alcohol level is at 0.10 or higher, above the legal limit of 0.08.
Langloss said there are cases where the tests can be inconclusive.
"There are people with natural nystagmus that is pretty distinctive," Langloss said. "For that reason, we don't just rely on one test."
Other field tests used during DUI stops are the one-leg stand, walk and turn, and having the person touch their finger to their nose. Two other tests, counting and reciting the alphabet, are also used in the field, though they are not standardized.
"If the person can't do a simple thing like saying the alphabet from A to Z, it's a pretty good indication that something is wrong," he said.
The National Highway Traffic Safety Administration says HGN tests have a 77 percent accuracy rate in identifying drunken drivers, making such tests the most reliable roadside test for drunkenness.
"Based on my training and experience, the test is very reliable," 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.
The decision places Illinois on a small list of states where the admissibility of HGN tests in DUI prosecutions has not been decided. According to a 2002 federal court decision that lists the status of the law in 43 states, HGN tests are not admissible in at least three - Kansas, Mississippi and Pennsylvania. In most others, courts have decided that juries can hear the results of HGN tests.
Whiteside County State's Attorney Gary Spencer said the admissibility of HGN testing is determined during a Frye hearing, held in front of a judge prior to the trial. During the hearing, expert testimony is heard to determine whether or not the test is generally accepted in the scientific community. Spencer said he believes the test is reliable, but it is only one piece of the puzzle.
"HGN testing is one thing under a whole umbrella of things that officers, the state's attorney's office and the court look at in DUI cases," Spencer said. "There are other things the arresting officer can use to determine if someone is drunk, such as observing erratic driving and other physical symptoms, such as staggering and slurred speech."
Whitcombe said the Frye hearings place the burden on the state when determining the admissibility of the test, which can both help and hinder the prosecution.
"It really depends on the case," Whitcombe said. "In the weaker cases, it will make a big difference. In cases where there is a lot of evidence, it's not going to make that much of a difference. It's just one piece of the puzzle."
Gatehouse News Service contributed to this report.