H.G.N. (Horizontal Gaze Nystagmus)

by Laine Means

This article is a condensed version of a paper written in partial fulfillment of the requirements for the class of Scientific Evidence and Opinion Testimony during the Winter Semester of 1999 at the UMKC School of Law. The extensive footnotes have been omitted.

  • Every year, tens of thousands of people die in traffic accidents. Alcohol is a major contributor in traffic fatalities. Alcohol is the most abused drug in the United States. The name "alcohol" is given to a family of closely related and naturally-occurring chemicals. Every chemical called "alcohol" is made up of molecules that contain a single oxygen atom and differing numbers of hydrogen and carbon atoms. Ingestible alcohol is known as ethyl alcohol or ethanol. Ethanol is the active ingredient in beer, wine and liquors which impairs driving. Approximately 43% of drivers killed in crashes have been drinking. Alcohol- related crashes are about nine times more likely to result in death than crashes without alcohol involvement. After drinking, drivers are more likely to take excessive risks, like speeding. Additionally, drinking drivers are more likely to have slowed reaction times resulting in the inability to slow down before crashing. Two percent of drivers, on average, on the road at any given time and driving while intoxicated.

  • To combat the serious consequences of driving under the influence, the National Highway Traffic Safety Administration ("NHTSA") has developed a battery of field sobriety tests, which are designed to detect the impaired driver. NHTSA considers the tests "the most effective procedure[s] for testing drivers at roadside to determine whether or not they are intoxicated." Many of the most reliable and practical psychophysical tests use the concept of divided attention. Divided attention requires an individual to concentrate on two things at once. Driving is an example of a divided attention task. A driver must simultaneously control steering, braking and acceleration, and react appropriately to changing conditions in order to operate a vehicle safely. Alcohol significantly reduces persons' ability to divide their attention between tasks. Even while under the influence, many people can handle a single, focused attention task fairly well, but cannot satisfactorily divide their attention to handle multiple tasks at once. Field sobriety tests that simulate the divided attention characteristics of driving are being used by police departments nationwide. The best tests use the same mental and physical capabilities that a person needs to drive safely: information processing; short-term memory; judgment and decision making; balance; steadiness, sure reactions; clear vision; small muscle control; and coordination of the limbs. Two divided attention field sobriety tests that have been proven accurate and effective in DWI Detection are the Walk-and-Turn and the One-Leg Stand.

  • An additional test is the horizontal gaze nystagmus ("HGN"). When used in combination with divided attention tests, HGN helps police officers correctly distinguish suspects who are under the influence of alcohol from those who are not. The test is based on the fact that alcohol affects the automatic tracking mechanisms of the eyes. Nystagmus is defined as "an involuntary rapid movement of the eyeball, which may be horizontal, vertical, rotatory, or mixed." Alcohol slows down the eyes' ability to rapidly track objects and causes to eyes to oscillate, or "jerk", before they normally would in a sober person. Alcohol stimulates the nerve endings, making nystagmus more pronounced in intoxicated persons. As a person's blood alcohol concentration increases, the eyes will "jerk" sooner as they move to the side. The HGN test claims to gauge intoxication by measuring the involuntary oscillation of the eyes.

  • The procedure to be used by police officers is set out by the National Highway Traffic Safety Administration in the DWI Detection and Standardized Field Sobriety Testing Student Manual. Prior to administration of HGN, the eyes are checked for equal tracking ability and equal pupil size. If the eyes do not track together or if the pupils are unequal in size, injuries or medical disorders are likely the cause of the nystagmus. The NHTSA standardized clues include lack of smooth pursuit, distinct nystagmus at maximum deviation and onset of nystagmus prior to reaching a 45 degree angle. Standardized administration procedures include: holding the stimulus 12-15 inches in front of the suspect's nose; keeping the tip of the stimulus slightly above the suspect's eyes; always moving the stimulus smoothly; always checking for all three clues in both eyes; starting with suspect's left eye; checking the clues in sequence: (1)lack of smooth pursuit, (2) distinct nystagmus at maximum deviation, (3) onset of nystagmus prior to 45 degrees; always checking for clues at least twice in each eye. The NHTSA manual indicates that no other "clues" are recognized by the NHTSA as valid indicators of HGN. In particular, the NHTSA does not support the allegation that onset angle can reliably be used to estimate BAC, and considers any such estimation to be misuse of the horizontal gaze nystagmus test. The NHTSA sets forth standardized criteria for evaluating HGN. The maximum number of clues of horizontal gaze nystagmus suspect can exhibit is six, occurring if the suspect exhibited all three clues in each eye. If a suspect exhibits four or more clues, it should be considered evidence that the suspect's BAC is above .10.

  • Nystagmus may be caused by many other factors. The court, in State v. Witte, 251 Kan. 313, 326, 836 P.2d 1110, 1119 (1992) said:

  • Nystagmus can be caused by problems in an individual's inner ear labyrinth. In fact, irrigating the ears with warm water or cold water...is a source of error. Physiological problems such as certain kinds of diseases may also result in gaze nystagmus. Influenza, streptococcus infections, vertigo, measles, syphilis, arteriosclerosis, muscular dystrophy, multiple sclerosis, Korsakoff's Syndrome, brain hemorrhage, epilepsy, and other psychogenic disorders all have been shown to cause nystagmus. Furthermore, conditions such as hypertension, motion sickness, sunstroke, eyestrain, eye muscle fatigue, glaucoma, and changes in atmospheric pressure may result in gaze nystagmus. The consumption of common substances such as caffeine, nicotine, or aspirin also lead to nystagmus almost identical to that caused by alcohol consumption. (Quoting Pangman, Horizontal Gaze Nystagmus: Voodoo Science, 2 DWI J. 1, 3-4 [1987])

  • Also, a individual's circadian rhythms or biorhythms can affect nystagmus readings. The body reacts differently to alcohol at different times in the day. Taking this into consideration, one researcher suggests the angle of onset should be decreased five degrees between midnight and 5 a.m. Rouleau, 4 Am.Jur. Proof of Facts 3d 439 � 9, p. 456; Pangman, 2 DWI Journal at 3.

  • The NHTSA manual recommends removal of all contact lenses. In addressing non-alcohol causes of nystagmus the manual only notes, "[n]ystagmus may be due to causes other than alcohol in three or four percent of the population." Critics argue that with the numerous causes of HGN listed above, that the instances of non-alcohol related HGN is greater than three to four percent. In 1990, the United States population was 248.71 million people. During that year, 22 million (8.4%) wore contact lenses. This alone indicates that significantly more that three to four of the population may have nystagmus unrelated to alcohol.

  • Conflict begins to arises when courts are asked to determine the admissibility of novel scientific evidence such as HGN. Initially, the court must ask if evidence is relevant. To be relevant, evidence must be probative of a material fact. If deemed relevant, the court must address whether the jury is familiar with the underlying science, as well is determine whether the "science" is valid. Most jurors are not familiar with HGN, requiring expert testimony to aid the jury in determining the test's probative value. Two main approaches have been taken in evaluating the validity of expert evidence on HGN.

  • "General acceptance" was established as the test in Frye v. United States, 293 F. 1013, 1014 (D.C. Cir. 1923), a case which involved the admissibility of polygraph tests:

  • Just when a scientific principle or discovery crosses a line between the experimental and demonstrable stages is difficult to define. Somewhere in this twilight zone the evidential force of the principle must be recognized, and while the courts will go a long way in admitting expert testimony induced 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.

  • In recent years, the United States Supreme Court has held that the Frye standard does not apply to the admission of scientific evidence in federal courts. The Court held that the Frye standard had been superseded by the passage of Federal Rule of Evidence 702 and that proof of scientific validity is to be the standard of admissibility. Daubert v. Merrell Dow Pharmaceuticals, 113 S. Ct. 2786 (1993). The decision set forth the following procedure to determine validity:

  • Faced with a proffer of expert scientific testimony, then, the trial judge must determine at the outset, pursuant to Rule 104(a), whether the expert is proposing to testify to (1) scientific knowledge that (2) will assist the trier of fact to understand or determine a fact in issue. This entails a preliminary assessment of whether the reasoning or methodology underlying the testimony is scientifically valid and of whether that reasoning or methodology properly can be applied to the facts in issue. Id. at 2796.

  • The Daubert court then suggested the trial judge consider several factors when determining the admissibility of expert testimony: (1) whether the evidence has been tested by scientific methodology, (2) whether the underlying theory or technique has been subject to peer review and has been published in professional literature, (3) how reliable the results are in terms of potential error rates and (4) general acceptance. Id. at 2796.

    Continuing debate on the differences between the two approaches--Frye and Daubert--has been noted and numerous state courts continue to use the Frye test despite possessing evidence rules patterned after the Federal Rules of Evidence. Additionally, the tests are not mutually exclusive. Under Daubert, general acceptance remains one factor probative of validity. Application of either the Frye or the Daubert test can lead to differing opinions on admissibility of HGN testimony.

    Research on HGN is limited. Only three published studies have tested HGN as a field sobriety test. The Southern California Research Institute (SCRI) study, entitled Development and Field Sobriety Tests of Pyschophysical Tests for DWI Arrests, DOT-HS-805-864 (1981) was commissioned by the National Highway Traffic Safety Administration. The study included a laboratory and field component. Due to lack of cooperation and poor performance by participating officers, SCRI concluded the field study data was not worthy of statistical analysis. After training, the control group arrested 28.6 percent of "stoppees" with BACs between .05 percent and .099 percent, while arrest rates in for other BACs remained the same. Therefore, officers made the wrong decision to arrest almost 30 percent of the time. This leads to the conclusion that arrests made based on HGN in suspected zone of .05 to .099 BAC are the most likely to produce most decision errors. SCRI recommended that a major effort was needed for a new field evaluation: "Extremely serious problems result when there is a lack of interest and cooperation by individual officers, by supervisory personnel, or by agencies."

  • The NHTSA then performed another study, Field Evaluation of a Behavioral Test Battery for DWI, DOT-HS-806-475 (1993). Officers from four different states were instructed to administer the test battery (walk-and-turn, one-leg-stand and horizontal gaze nystagmus) and also to administer a preliminary breath test (PBT) to every stoppee. The report did not specifically provide data on HGN, but reported on the combined procedure. NHTSA claimed an accuracy rate for the combined procedure of 82 percent, with 16 percent false positives and 1 percent false negatives. The NHTSA's report cautioned against using the data as indicative of the accuracy of the tests because only stoppees asked to participate in breath tests were included in the data. This factor makes the group sample biased toward high BAC levels because it did not include all stoppees, it included only those actually arrested. Additionally, the study did not provide the actual BAC of those arrested. Without knowing the sample distribution, any accuracy rate becomes suspect, particularity when the probability of error is greatest near the legal limit.

  • A third study was conducted by George Golding and Robert Dobie, Gaze Nystagmus and Blood Alcohol, 96 LARYNGOSCOPE 713 (1986). It evaluated 159 DWI suspects and 46 emergency room patients. Seattle Police officers performed the field evaluation to only those they suspected of driving under the influence of alcohol, again biasing the data towards high BACs. Eight of the 159 had a BAC of less than .10, three of which the officers classified as legally intoxicated.

  • Researchers have conclude that the percentages generally cited by court opinions in support of HGN only exist in NHTSA publications. Joseph R. Meaney, Horizontal Gaze Nystagmus: A Closer Look, 36 Jurimetrics J.383, 385 (1996). The figures have not been duplicated in field study. The three studies all conclude that HGN can help officers decide whether a stop is a good candidate for arrest and subsequent chemical testing. The three tests also conclude that HGN should only be used as a tool raising or lowering suspicion of a person's sobriety. Officers in the field have not been able to show that they can correctly identify those drivers with actual BACs in the critical range of .05-.15 percent.

  • The NHTSA states that if nystagmus is observed at the 45 degree angle, a BAC of .10 can be correctly estimated 77 percent of the time. Alternatively, this indicates that results of HGN are incorrect 23 percent of the time. One researcher indicates that 50-60 percent of sober individuals who deviate their eyes more than 40 degrees to the side will exhibit nystagmus, and this type of nystagmus is indistinguishable from alcohol induced nystagmus. Pangman, 2 DWI Journal at 2 (citing Toglia, Electronystagmography: Technical Aspects and Atlas [1976]).

  • Several courts have taken these concerns regarding the scientific basis and validity of HGN, peer review, error rates and general acceptance into consideration when determining whether its admissibility as scientific evidence. In Witte, the court held that HGN test results could not be admitted into evidence at a DUI trial because the Frye standard had not been met. State v. Witte, 251 Kan. 313, 836 P.2d 1110 (1992) Oklahoma courts agreed, stating HGN does not met Frye requirements. See Yell v. State, 856 P.2d 996 (Okla. App. 1993). The Criminal Court of Appeals in Oklahoma stated "a review of the record in the present case reveals that there was absolutely no evidence that the reliability of the HGN test has gained acceptance in the concerned scientific community." In State v. Borchardt, 395 N.W.2d 551 (Neb. 1986), the court came to a similar conclusion. The court held that it was error to admit HGN test results into evidence at a DUI trial because the state had not established the scientific reliability of the test by laying a proper foundation.

  • By contrast, the majority of states seems to accept HGN testimony. One court held that acceptance was predicated on general acceptance within the relevant scientific communities of optometry, neurology, behavioral psychology, highway safety and forensic science. State v. Carlson, 45 Conn.Supp. 461, 720 A.2d 886 (1998). Another court held simply that HGN testimony was not "scientific" evidence, therefore did not need to satisfy Frye criteria, and results of the test were admissible the same as evidence of other field sobriety tests, such as finger-to-nose, or walk-and turn results. State v. Bresson, 51 Ohio St. 3d. 123, 554 N.E.2d 1330 (1990).

  • Perhaps the best approach to the dilemma of the non-existent proof of reliability of the determination of a specific blood-alcohol level by HGN is to admit the evidence, assuming the test was conducted in the prescribed manner by a properly trained police officer, to show impairment, but not as evidence of a specific blood-alcohol level.

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