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How is the HGN test used in Illinois DUI investigations?

Drivers who have been stopped by law enforcement officers in Illinois who have a reasonable suspicion that they are driving under the influence (DUI) will be asked to submit to tests meant to help an officer determine their level of impairment.

One of those tests is horizontal gaze nystagmus (HGN). In Illinois DUI law, this test is useful only to demonstrate the presence of alcohol or drugs, but not to demonstrate a level of impairment. Nystagmus is defined as being an involuntary jerking or bouncing of a person's eyeball related to a problem with the inner ear or the oculomotor control of of a person's eye. HGN therefore refers to a lateral or horizontal jerking when the eye gazes to the side. In the context of impaired driving, the consumption of alcoholic beverages or the consumption of certain other central nervous system depressants, inhalants or phencyclidine, the ability of the brain is unable to control the muscles of the eye. Theoretically, as the degree of impairment increases, the jerking or bouncing becomes greater. Neither is exactly true, as many possible causes of nystagmus exist that have nothing to do with impairment due to alcohol or any substance.

The attorneys at Fagan, Fagan & Davis focus on Illinois legal defense including challenging HGN evidence in driving under the influence (DUI) cases at courthouses in Cook County, Lake County and DuPage County.

HGN developed by NHTSA

The National Highway Traffic Safety Administration (NHTSA) has regulated all matters related to traffic safety since 1977, including a variety of field sobriety tests (FSTs). As a result, NHTSA has warned law enforcement officers DUI suspects should be positioned so that they are not facing blinking police cruiser lights or the lights of oncoming traffic. Those lights can result in false optokinetic nystagmus readings. While HGN is one of three FSTs that can be used by law enforcement officers, the other two tests are the walk-and-turn test and the one-leg-stand test.

Some trial courts across the country do not admit into evidence HGN test results as prosecutors have not been able to satisfy evidentiary standards regarding scientific or technical evidence. The Illinois Supreme Court addressed issues regarding the admissibility of HGN evidence at trial is a February 2010 ruling.

In that case the defendant argued to the court that the use of HGN evidence should be limited to a preliminary means of establishing probable cause for the arrest. The defendant asserted that an HGN test does not prove impairment beyond a reasonable doubt. The Supreme Court's opinion said that the testimony of the law enforcement officer regarding the results of a failed HGN test "tends to show that he or she consumed alcohol prior to being tested. Similarly, testimony that a defendant did not display any sign of HGN is relevant evidence that tends to show that he or she had not consumed alcohol. The result of the test, therefore, makes it either more or less likely that a defendant was impaired due to alcohol. This is the concern addressed by the trial court's conclusion that the use of HGN evidence should be limited to proof of alcohol consumption and the possibility of resulting impairment. A trial Court can sustain an objection to certain questions or arguments made by the prosecutor, giving a limiting instruction at the time the testimony is given, or giving a written jury instruction at the conclusion of the case. "The need for a limitation on the use of the evidence, however, is not a basis for finding the evidence inadmissible at trial under the test of Frye. We, therefore, reject defendant's invitation to limit the use of this relevant piece of evidence to showing probable cause."

Frye v. United States

In 1923, the Court of Appeals for the District of Columbia held in Frye v. United States that for new or novel scientific evidence to be admissible, it must "have gained general acceptance in the particular field in which it belongs." This standard came to be known as the Frye standard. Technically there are two prongs to the Frye standard:

  • identifying the "particular field" or relevant scientific community; and
  • demonstrating that novel scientific evidence (such as the HGN test) is generally accepted in that community.

Combined, both prongs provided a measure of the reliability of the scientific evidence.

In 1993, the U.S. Supreme Court held in Daubert v. Merrell Dow Pharmaceuticals, Inc. that the Federal Rules of Evidence (FRE), specifically Rule 702, replaced the common law Frye standard as the evidentiary basis for admitting scientific evidence in federal courts. The Supreme Court found that Rule 702 does not incorporate the general acceptance requirement of the Frye standard, as a prerequisite for the admission of expert scientific testimony.

The Illinois Supreme Court also found the trial court might rule HGN evidence to be inadmissible on grounds of undue prejudice. The defendant in the 2010 case also asserted that oversight of law enforcement officers who administer the HGN test in the field is insufficient. The defendant also argued that law enforcement officer should receive extensive training and that stricter standards regarding the procedure for performing the test in the field should be imposed and that the only acceptable method for administration of the HGN test is the NHTSA method. The court's opinion suggested that this argument merged two questions of concern. The first question is the proper method for conducting HGN testing in the field. The second question centers on the qualifications of the witness called to testify regarding the results of an HGN test.

Proper training for HGN

In terms of the general acceptance of the NHTSA roadside HGN test the evidence presented by both parties to the trial court was geared towards the test as it has been developed and taught. The Supreme Court held that "evidence of HGN field sobriety testing, when performed according to the NHTSA protocol by a properly trained officer, is admissible under the Frye test for the purpose of showing whether the subject has likely consumed alcohol and may be impaired." Regarding the qualifications of the individual witness, the court said that "a properly trained police officer who performed the HGN field test in accordance with proper procedures may give expert testimony regarding the results of the test. We also agree with the trial court's conclusion that a testifying officer may use the HGN test results as a part of the basis for his opinion that the defendant was under the influence and impaired."

The Illinois Supreme Court was asked to consider whether a new trial on the DUI charges would subject defendant to double jeopardy. The court agreed that a new trial is proper and that there is "no bar to the officer's testifying regarding the facts and circumstances he observed while investigating the accident. In addition, the officer's opinion regarding defendant's state of intoxication was supported by other facts in the record, aside from her performance on the HGN test." And, the court ruled "that while the admission of the HGN test results in this case was error, it was error because the state did not lay the proper foundation, not because HGN test results are inadmissible in general." The court concluded that "the admissibility of HGN evidence in an individual case will depend on the state's ability to lay a proper foundation and to demonstrate the qualifications of its witness, subject to the balancing of probative value with the risk of unfair prejudice."

The attorneys at Fagan, Fagan & Davis have defended countless clients against DUI charges throughout the Chicago area courts, including those located in Cook County, DuPage County and Lake County. The attorneys at Fagan, Fagan & Davis understand which defense strategies are the most effective in court and how to challenge evidence gathered by law enforcement and offered by the prosecution. Contact us now for a free consultation.

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