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DWI Journal (Law & Science)
December, 1988

By Kathleen Colton
The phenomenon of horizontal gaze nystagmus, or jerking of the eyeball, may be validly measured in a laboratory, but becomes pseudoscience when employed by a police officer under roadside conditions and used to support a judgment that the subject is under the influence of alcohol. Unless forcefully opposed, the test may be an effective tool to convince a jury of a defendant’s guilt.

In this article, the author presents an approach to conducting a motion in limine to bar introduction of HGN test results and expert testimony as to the test’s reliability. She fleshes out the important areas of questioning and notes the many possible alternative causes of nystagmus besides alcohol. The inaccuracy of roadside testing and the high rate of false positives further combine to create formidable grounds for exclusion. — Editor’s note.

HGN test popular with police

The Horizontal Gaze Nystagmus Test (HGN), which purports to establish a correlation between the angle of onset of involuntary jerking of the subject’s eyes and blood alcohol content, has be come an enormously popular field sobriety test since its introduction in the western United States in the early 1980s. Once used only as an experimental test, the HGN has come to be regarded by law enforcement personnel as an easy and efficient way to determine at roadside if a driver’s blood alcohol content is at .10 or above.

A recent Illinois case demonstrates that a motion in limine can be effectively conducted to prohibit introduction of the test results and expert testimony concerning the test before ever getting to trial in a drunk driving prosecution.

In order to make a successful motion, it is first important to have a layperson’s grasp of the medical condition known as nystagmus. Understanding its causes allows the defense attorney in a drunk driving prosecution to attack the reliability of the HGN test as an indicator of blood alcohol content. While it is probably rare that the state will rest its entire case on introduction of the test as proof of intoxication, the Illinois case proves that that possibility does indeed exist.

For the defense attorney who is faced with more evidence of intoxication in a particular case, elimination of the introduction of the HGN test results will deprive the state of an influential jury tool. Proceeding upon the premise that nystagmus is a neurological condition which is often unrelated to the consumption of alcohol will bolster the argument against its reliability.

Definition of nystagmus

The Manual of Ophthalmic Terminology (1982) defines nystagmus as “the oscillating movement of the eyeball which may be horizontal, vertical, rotatory, or mixed. It may be congenital or acquired; pendular or jerky.”

The HGN test attempts to measure only the horizontal jerking of the eyeball by approximating the angle at which the movement begins (the angle of onset). The angle of onset is then said to correlate to a subject’s blood alcohol content; the most frequent figure used to correlate to .10% BAC is n onset angle of 45 degrees.

Gary A. Lesher, Ph.D., associate professor of pharmacology at the Illinois College of Optometry in Chicago, was the witness whose testimony the state attempted to introduce in People v. Dakuras, 527 N.E.2d 163 (lll.App. 2 Dist. 1988).* The defendant in the case was physically disabled due to illness, and had refused to submit to either a breath test or chemical analysis. The results of the HGN test there fore comprised the state’s entire case regarding proof of intoxication.

Condition common regardless of alcohol intake

Dr. Lesher had supervised a study on the HGN and its correlation with blood alcohol content con ducted at the Illinois College of Optometry in 1986. Dr. Lesher testified that” ... the physiologic control of eye movement is a neurological function, a coordinated effort of the muscles and nervous tissues, and. the HGN depends upon the disruption of the coordinated muscular neurologic activity. Alcohol and some other drugs that are also central nervous system depressants tend to disrupt that normal coordinated movement. This is then observed in the test, the HGN, and work has shown could be correlated with the level of alcohol in the body.” (transcript of motion, page 9).

Dr. Lesher further testified that some 50 to 60 per cent of the general population have “physiologic end point nystagmus,” and involuntary jerking of the eyeball once the eyes are moved from a normal gaze to an extreme lateral position (as is done during administration of the HGN test). This 50-60 percent figure has been noted in other HGN studies, with the angle of onset of the jerking occur ring anywhere from 30 to 40 degrees, regardless of alcohol consumption.

There also exists a small percentage of the general population which has naturally occurring nystagmus present even when the eyes are in normal, straight-ahead gaze position. This nystagmus has organic causes and is referred to as synchronous nystagmus.

It is important to note here that past National Highway Transportation Safety Administration (NHTSA) studies recognized nystagmus in subjects who had not consumed alcohol, but this naturally occurring nystagmus was statistically dismissed. The NHTSA apparently assumed that control subjects with organic nystagmus had consumed some other drugs which accounted for the condition. See Pangman, “HGN: The New Drunk Driving Alchemy,” 11 The Champion 2 at 6-11 (April 1987); Pangman, “Horizontal Gaze Nystagmus: Voodoo Science,” 2 D WI Journal: Law & Science 3 (March 1987). The natural occurrence of nystagmus thus be comes another basis on which to attack the reliability of the HGN test as an indicator of blood alcohol content.

Questions the defense should ask the expert

The defense attorney should bolster this argument with questions about other causes of nystagmus. The medical literature available lists conditions and substances, which, apart from alcohol consumption, account for nystagmus at varying angles of onset. Anyone attempting to testify in an expert capacity about the test should be asked about the effects of the following: diseases such as multiple sclerosis, glaucoma, cataracts, Parkinson’s disease, chronic alcoholism, hypertension, inner ear problems, and brain tumors; drugs such as barbiturates, antihistamines, phencyclidine (PCP), anticonvulsants, depressants, aspirin, streptomycin, nicotine, and caffeine; conditions including the subject’s fatigue factor and physical condition. In addition, all of the studies conducted advise removal of prescription lenses, including hard contact lenses. The ability to focus clearly on the object being followed by the eyes is alleged to have no effect on a subject’s ability to perform the test, but extreme near-sightedness and far-sightedness should also be brought into question.

Head must be stationary

Also important in conducting the test is the ability of the subject to keep his head in a stationary position while the test is being performed. Movement of the head impedes the ability of the person administering the test in determining when a 45 degree angle has been reached (the magic angle at which the onset of jerking is said to correlate to .10% BAC).

All of the laboratory tests conducted on the HGN have been performed upon subjects whose heads were absolutely stationary due to the use of chin rests and elaborate arc perimeter machines. The Instructor’s Manual issued by the Illinois Local Government Law Enforcement Officers Training Board advises: “if the suspect keeps moving head, have him cup his chin with his hands.” Other manuals advise using an officer’s flashlight as a chin rest. It may be appropriate to question a testifying expert concerning the effects of roadside conditions on the outcome of the test.

Another factor relating to the reliability of the HGN test is the actual training of the person ad ministering the test. While law enforcement training will vary from state to state, it appears that most officers are trained first in the basics of the condition known as nystagmus. The Field Sobriety Testing instructor Manual of the Police Traffic Services Training Project of the State of Illinois begins by introducing officers to the various kinds of physiological and neurological nystagmus, acknowledging that a certain portion of the population will be found to have forms of naturally occurring nystagmus unrelated to alcohol consumption.

Attacking the estimate of angle

Officers are then advised to disregard all forms of nystagmus except the horizontal gaze variety (while being warned that knowledge of the other forms of nystagmus may come in handy when testifying in court). Officers are instructed in the “smooth pursuit” method and are advised that the magnitude of the eye’s return movements when following an object such as a penlight result in jerking motions when a subject is under the influence of alcohol. Once the magnitude of the jerking motions reaches the “correct” angle of onset, officers are instructed that a correlation exists between the movements and blood alcohol content. All that is left, then, is instruction concerning determination of the 45 degree angle.

Many of the manuals advise using a template to instruct officers in the determination of a 45 degree angle; practice with the template soon gives way to practice on a partner, until the officer feels comfort able with his own estimation of the angle. Once in the field, usually under nighttime conditions, officers are expected to determine correctly’ the angle of onset of the nystagmus, and then to correlate that angle with the subject’s blood alcohol content. it is important to remember that under laboratory conditions a stationary subject’s angle of onset is measured exactly, often through the use of an arc perimeter machine. No such exacting standards are met in the field.

High false positive rate

After having established through questioning the many possibilities for error in the administration of the HGN test, perhaps the strongest weapon still remains to the defense attorney: the false positive percentage found in laboratory studies of the test. Dr. Lesher, testifying in People v. Dakuras, stated that 23 percent of the 84 subjects in his study showed an angle of onset of less than 45 degrees when, in fact, their blood alcohol levels were shown to be less than .10 percent upon breathalyzer examination.

In its ruling on the motion in limine, the court noted the importance of such an error ratio in a criminal case. The other studies available also found such a false positive factor, ranging to as low as 3 percent. See Tharp, V., Burns, M., Moskowitz, H., ‘Development and Field Test of Psychophysical Tests for DWI Arrest,” DOT HS-805-864 (March 1981), Burns and Moskowitz, ‘Psychophysical Tests for DWI Arrest,” DOT HS-802-424 (June 1977). The ideal laboratory conditions under which all of these tests are conducted is a point to be stressed.

Scientific criteria unmet

Finally, it is important to stress lit argument that the HGN test does not meet the Frye standard of general acceptance in the scientific community. Frye v. United States, 293 F. 1013, D.C. Cir. 1923. The court stated:

Just when a scientific principle or discovery crosses the line between the experimental and demonstrative stages is difficult to define. Some where in this twilight zone the evidential force of the principle must be recognized, and while courts will go a long way in admitting expert testimony deduced from a well-recognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs.

While many of the studies commissioned by NHTSA purport to prove the reliability of the HGN test as an accurate indicator of blood alcohol con tent, other studies exist which show the test’s potential for inaccuracy (Norris, 25 Journal of Forensic Sciences Society 476, 1985), bolstering the argument that the HGN test is still not generally accepted in the scientific community. For an analysis of the various jurisdictions’ approaches to the admissibility of HGN results, see Tarantino, Defending Drinking Drivers, §536.8 (2d Ed. 1986, 1988 Supp.); Annot., Horizontal Gaze Nystagmus Test: Use in Impaired Driving Prosecution 60 ALR 4th 1129 (1988).

General acceptance in the law enforcement community should not be enough to persuade a court to accept either testimony about the test’s accuracy or the test results as proof of intoxication. Every effort should be made pre to avoid the introduction of HGN results, a very valuable jury tool for the state.

Kathleen Colton was working for the Office of Public Defender in DuPage County, Illinois when she success fully conducted the motion for People v. Dakuras. She is a member of the National Association of Criminal Defense Lawyers and the Illinois Attorneys for Criminal Justice.

(* The Illinois appellate court actually decided that HGN results were inadmissible on grounds other than those argued by the parties in the motion in limine. The court determined that only results of chemical analyses were admissible under the Illinois drunk driving statutes and that since the HGN test was not a chemical analysis, but rather a field sobriety test, its results were inadmissible. — Editor.)