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The HGN test and supposed observations can be some of the most dangerous pieces of the State’s case when you have been charged with driving under the influence. However, experienced DUI trial attorneys understand that HGN test evidence can be effectively challenged. In order to effectively challenge the conclusions drawn from HGN test evidence, you must know what the HGN test in DUI cases is intended to do. It is an attempt to observe in a DUI suspect, how the test is supposed to be performed, and what the limitations of the test are.

Procedures of Horizontal Gaze Nystagmus Testing: The Three Clues in the HGN Test

The HGN Test

  • Nystagmus= involuntary bi-phasic movement of the eyes seen as a slow(er) drifting movement of the eyes away from the point of visual fixation followed by a quick(er) movement returning to the point of visual fixation.
  • Many different types of nystagmus:
    1. the type involved in field sobriety testing is HGN
    2. it represents the status of the central nervous system (CNS).
    3. At a threshold level for the individual, alcohol can cause HGN to be present.
  • Vertical nystagmus, it should be noted, is a different phenomenon with different causes.
    • The relevance of vertical nystagmus is primarily to indicate the presence of a neurologic crisis in the mid brain portion of the central nervous system.

  • ADMINISTRATION OF HGN REVIEW –
    1. To administer the HGN test, the officer instructs the suspects (test subject), “keep your head still, head straight ahead and follow the target object with your eyes.”
    2. officer then moves a finger, pencil, pen or other suitable target from the center of the head steadily toward one side then the other side in the prescribed test sequence.
    3. target is held 12-15” directly in front of the test subject.
      1. 4 components to the HGN test:
        • check for equal tracking;
        • check for smooth pursuit;
        • distinctnystagmus at maximum gaze and
        • onset of nystagmus at or before 45 degrees.
      2. Evaluation of the eyes creates confusing eye movements that can stimulate the clues sought during the HGN test.
      3. PASS DEFINED – A pass consists of moving the target, in a straight line, from the midline (center) to either the left or right as far as the end of visual gaze and back to the midline.
  • Equal tracking of the eyes and simultaneous evaluation for equal pupil size are the preliminary first 2 passes of the HGN test’s 14 passes
    1. to alert the officer to obvious presence of neurological symptoms that may require immediate medical attention.
  • EXCEPT FOR EQUAL TRACKING – rest of the passes are done in duplicate.
  • Checking for lack of smooth pursuit is done by repeating this sequence of the passes:
    1. midline to right back to midline then to left and back to midline.
    2. Each clue of the six clues in the HGN test has two passes plus the two passes of the preliminary check for equal tracking resulting in the total of 14 passes for a HGN test.
  • The presence or lack of smooth pursuit is the first set of clues in the HGN matrix of three clues per eye for a total of six clues for each HGN test result.
    1. Speed of the target is critically in this phase of the HGN test.
    2. Lack of smooth pursuit can be caused by a target moved too fast.
    3. Smooth pursuit, or lack thereof, is seen when a target is moved between 20-30 degrees per second. This means that covering the distance from mid line to the end of visual gaze (approximately 80 degrees) should take 3-4 seconds in each direction. That is 6-8 seconds for each pass.
      1. Lack of smooth pursuit is seen as a horizontal jerking motion of the eyes as the eyes jump from one point of visualization to another. This jumping motion is known as saccadic movement.
  • Next clue checked is distinct nystagmus at maximum gaze.
    1. target is held at the point of gaze where the eyes no longer move laterally from the midline;
    2. held at this location for a minimum of four seconds before scoring the clue.
    3. After 4 seconds, if there is nystagmus present a clue is scored for that eye when confirmed by the second pass (observation).
  • last clue in the HGN test is nystagmus at or before 45 degrees.
    1. The target is slowly moved from the mid line literally until nystagmus is observed.
    2. At the point of observation the target is stopped to make sure that there really is nystagmus present.
    3. The current location of the 45 degrees line is defined by the diagonal line created by a square formed when the distance of the target from the subject’s face is projected laterally.
    4. The eyes of a person under the influence of alcohol will show nystagmusonset at a lower angle as their blood-alcohol concentration (BAC) increases.
      1. Attempts have been made to approximate the BAC from the measured angle of onset. This is referred to as Tharp’s equation where the
        • angle of onset is subtracted from 50 and the result is the approximate BAC expressed as a decimal and a percentage.
        • Although it lacks scientific validity it is not uncommon to have an officer to attempt to testify to the BAC level using this formula. Accordingly the defense counsel may want the nystagmus evidence admitted if the nystagmus began at 45 degrees indicating a BAC of only 0.05%.
  1. The Lack of Smooth Pursuit (Clue #1) – The eyes can be observed to jerk or “bounce” as they follow a smoothly moving stimulus, such as a pencil or penlight.
    1. The eyes of an unimpaired person will follow smoothly, i.e., a marble rolling across a smooth pane of glass, or windshield wipers moving across a wet windshield.
  2. Distinct and Sustained Nystagmus At Maximum Deviation – (Clue #2) Distinct and sustained nystagmus will be evident when the eye is held at maximum deviation for a minimum of 4 seconds.
    1. People exhibit slight jerking of the eye at maximum deviation, even when unimpaired, but this will not be evident or sustained for more than a few seconds. When impaired by alcohol, the jerking will be larger, more pronounced, sustained for more than four seconds, and easily observable
  3. Onset of Nystagmus Prior To 45 Degrees (Clue #3) – The point at which the eye is first seen jerking. If the jerking begins prior to 45 degrees it is evident that the person has a BAC above 0.08, as shown by recent research.

Officers are trained that the the higher the degree of impairment, the sooner the nystagmus will be observable. There is no scientific basis for this conclusion.

Estimating a 45-Degree Angle

  1. How far you position the stimulus from the suspect’s nose is a critical factor in estimating a 45-degree angle, (i.e., If the stimulus is held 12″ in front of the suspect’s nose, it should be moved 12″ to the side to reach 45 degrees. Likewise, if the stimulus is held 15″ in front of the suspect’s nose, it should be moved 15″ to the side to reach 45 degrees.)

PROCEDURE

  • “I am going to check your eyes.”
  • “Keep your head still and follow this stimulus with your eyes only.”
  • “Keep following the stimulus with your eyes until I tell you to stop.”
  1. LACK OF SMOOTH PURSUIT –
    1. Move the stimulus smoothly, at a speed that requires approximately two seconds to bring the suspect’s eyesfar to the side as it can go.
    2. While moving the stimulus, look at the suspect’s eye and determine whether it is able to pursue smoothly.
  • Movement of the stimulus should take approximately two seconds out and two seconds back for each eye.
  1. Repeat the procedure.
  1. for distinct and sustained nystagmus at maximum deviation – beginning with the suspect’s left eye.
    1. Simply move the object to the suspect’s left side until the eye has gone as far to the side as possible. Usually, no white will be showing in the corner of the eye at maximum deviation.
    2. Hold the eye atthat position for a minimum of four seconds, and observe the eye for distinct and sustained nystagmus.
  • Repeat the procedure.
    • Fatigue Nystagmus. This type of nystagmus may begin if a subject’s eyes are held at maximum deviation for more than 30 seconds.
  1. onset of nystagmus prior to 45 degrees –
    1. Start moving the stimulus towards the right (suspect’s left eye) at a speed that would take approximately four seconds for the stimulus to reach the edge of the suspect’s shoulder.
    2. Watch the eye carefully for any sign of jerking.
  • When you see it, stop and verify that the jerking continues.
  1. Now, move the stimulus to the left (suspect’s right eye) at a speed that would take approximately four seconds for the stimulus to reach the edge of the suspect’s shoulder.
  2. Repeat the procedure.
    • It is important to usethe full four seconds when checking for onset of nystagmus. If you move the stimulus too fast, you may go past the point of onset or miss it altogether.
    • If the suspect’s eyes start jerking before they reach 45 degrees, check to see that some white of the eye is still showing on the side closest to the ear. If no white of the eye is showing, you either have taken the eye too far to the side (that is more than 45 degrees) or the person has unusual eyes that will not deviate very far to the side.
  3. Nystagmus may be due to causes other than alcohol. These other causes include seizure medications and some other drugs. A large disparity between the performance of the right and left eye may indicate a medical condition.
  4. Based on the original research, if you observe four or more clues it is likely that the suspect’s BAC is above 0.10. Using this criterion you will be able to classify about 77% of your suspects accurately. This was determined during laboratory and field testing and helps you weigh the various field sobriety tests in this battery as you make your arrest decision.
  • Only validated to indicate for a specific BAC
  • Caused by DID drugs
  • Medical Impairment• Resting Gaze Nystagmus, Equal Pupil Size, Equal Tracking
  • Officers are reminded to ask questions about the subject’s eyes and general health conditions prior to administering the HGN test.

ROBUSTNESS OF HGN (2007)

Study was done in reference to defense arguments

Stimulus Speed

1 second and 2 seconds Stimulus Height

0 inches, 2 inches, and 4 inches Stimulus Distance

10 inches, 12 inches, 20 inches

ROBUSTNESS OF HGN (2007)

When administered CORRECTLY!!!

67% < 0.08 had 4/6 clues or more
65% < 0.05 had 4/6 clues or more
85% (6/7) < 0.03 had 4/6 clues or more 6/6 observed at BAC of 0.029

Stimulus Too High

91% < 0.08 had 4/6 clues or more 90% < 0.05 had 4/6 clues or more

ROBUSTNESS OF HGN (2007)

HGN is a robust procedure

4 clues can be 0.03 BAC and above 6 clues can be 0.06 BAC and above

SAN DIEGO (1998)

The False Positives

37% < 0.08 had 4/6 clues or more on HGN 52% < 0.08 had 2/8 clues or more on WAT

41% < 0.08 had 2/4 clues or more on OLS 28% < 0.08 were estimated to be over

The Court of Special Appeals of Maryland has judicially recognized 38 non-alcohol-related causes of Horizontal Gaze Nystagmus. They include:

  1. Problems with the inner ear labyrinth;
  2. Irrigating the ears with warm or cold water under peculiar weather conditions;
  3. Influenza;
  4. Streptococcus infection;
  5. Vertigo;
  6. Measles;
  7. Syphilis;
  8. Arteriosclerosis;
  9. Muscular dystrophy;
  10. Multiple sclerosis;
  11. Korsakoff’s syndrome;
  12. Brain hemorrhage;
  13. Epilepsy;
  14. Hypertension;
  15. Motion sickness;
  16. Sunstroke;
  17. Eyestrain;
  18. Eye muscle fatigue;
  19. Glaucoma;
  20. Changes in atmospheric pressure;
  21. Consumption of excessive amounts of caffeine;
  22. Excessive exposure to nicotine;
  23. Aspirin;
  24. Circadian rhythms;
  25. Acute trauma to the head;
  26. Chronic trauma to the head;
  27. Some prescription drugs, tranquilizers, pain medications, anti­convulsants;
  28. Barbiturates;
  29. Disorders of the vestibular apparatus and brain stem;
  30. Cerebellum dysfunction;
  31. Heredity;
  32. Diet;
  33. Toxins;
  34. Exposure to solvents, PCBs, dry-cleaning fumes, carbon monoxide;
  35. Extreme chilling;
  36. Eye muscle imbalance;
  37. Lesions;
  38. Continuous movement of the visual field past the eyes, i.e., looking from a moving train; and
  39. Antihistamine use.

Limiting the use of the HGN Test in Georgia DUI Refusal Cases

In Georgia DUI cases, the HGN test (sometimes called the “eye test”) can be one of the primary pieces of evidence that the state relies upon.  One of the primary areas of cross-examination that I focus upon with regard to the HGN test is the lack of correlation between the HGN test and a person’s actual driving ability.  However, this is frequently addressed by the state by questioning an officer about the correlation between the HGN test and a suspect’s BAC, and many will attempt to ask the officer if he has observed a correlation between the results on the HGN test subjects that did submit to the breath test in his cases.  Below is a motion that you can use to limit this type of testimony by an officer:

MOTION IN LIMINE TO LIMIT OFFICER’S TESTIMONY REGARDING CORRELATION BETWEEN THE HORIZONTAL GAZE NYSTAGMUS TEST AND BREATH TEST RESULTS

Comes Now, the Defendant in the above-styled case, by and through the undersigned counsel of record, and respectfully moves this Honorable Court to limit the arresting officer’s testimony regarding the horizontal gaze nystagmus (HGN) and breath test results in other cases.  In support of his motion, the Defendant shows this Honorable Court the following:

The Defendant was arrested on July 28, 2007 by XXXXXXXX of the XXXXXXXX.  In connection with his investigation of the Defendant, XXXXXXXXX performed the HGN test upon the Defendant.  The Defendant requests that the Trooper be precluded from offering any testimony regarding any alleged correlation between observations during the HGN test and breath tests results obtained in other cases.

The determination of whether a scientific principle or technique is admissible in criminal case in Georgia is governed by the rule stated in Harper v. State, 249 Ga. 519, 525-26, 292 S.E.2d 389 (1982).  The Harper rule requires that the Court in a criminal case determine “whether a given scientific principle or technique is a phenomenon that may be verified with such certainty that it is competent evidence in a court of law….”  Id. at 525.  Otherwise stated, the Court must determine whether the scientific principle or technique “has reached a scientific stage of verifiable certainty” or “‘rests upon the laws of nature.’”  Id. (citations omitted).  “[E]vidence based on a scientific principle or technique is admissible only if the science underlying the evidence is a phenomenon that may be verified with such certainty that it is competent evidence in a court of law.”  Parker v. State, 307 Ga.App. 61, 704 S.E.2d 438 (2010).

In Harper, the Georgia Supreme Court described the types of evidence that our trial courts should look to in determining whether a scientific principle or technique has reached a scientific stage of verifiable certainty.  The Harper court explicity expressed its disapproval of the “counting heads” rule of Frye v. United States, 293 F. 1013 (D.C. Cir. 1923).  Id.  According to the Harper Court:

The trial court may make this determination from evidence presented to it at trial by the parties; in this regard expert testimony may be of value. Or the trial court may base its determination on exhibits, treatises or the rationale of cases in other jurisdictions. The significant point is that the trial court makes this determination based on the evidence available to him rather than by simply calculating the consensus in the scientific community. Once a procedure has been recognized in a substantial number of courts, a trial judge may judicially notice, without receiving evidence, that the procedure has been established with verifiable certainty, or that it rests upon the laws of nature.

Id. at 525-26.  “[O]nce a procedure has been utilized for a significant period of time, and expert testimony has been received thereon in case after case, the trial court does not have to keep reinventing the wheel; a once novel technology can and does become commonplace.”  Hawkins v. State, 223 Ga. App. 34, 476 S.E.2d 803, 807 (1996).

Certain evaluations commonly employed in DUI investigations, such as the “ABCs,” the “Walk-and-Turn Test,” and the “One-Leg Stand Test,” have been recognized as “physical dexterity exercises that common sense, common experience, and the ‘laws of nature’” share are performed less well after drinking alcohol.”  Hawkins v. State, 223 Ga. App. 34, 476 S.E.2d 803, 807 (1996).  Accordingly, “[t]he screening of these gross motor skills is hardly the type of ‘scientific principle or technique’ to which Harper referred, and this Court will not hold these physical manifestations of impairment, which could be as obvious to the layperson as to the expert, to such a standard of admissibility.”  Id.

In contrast to those tests which test gross motor skills (e.g., a walk-and-turn or one-leg stand test) or which drawn upon commonsense for their utility in a DUI investigation (e.g., an alphabet test), certain tests typically employed in DUI investigations require a determination that the Harper standard has been satisfied.  In Hawkins, the Court of Appeals clarified that the horizontal gaze nystagmus (hereinafter, “HGN”) test is a scientific test that required a Harper foundation. The HGN test involves “the well-known and medically accepted principle that nystagmus can be caused by the ingestion of alcohol: ‘Jerk nystagmus … is characterized by a slow drift, usually away from the direction of gaze, followed by a quick jerk of recovery in the direction of gaze.  A motor disorder, it may be congenital or due to a variety of conditions affecting the brain, including ingestion of drugs such as alcohol and barbiturates….’”  Hawkins, 476 S.E.2d at 807 (citations omitted).

Any alleged correlation between HGN and a breath test result in other cases certainly does not rest upon “common sense, common experience, and the ‘laws of nature[.]’”  Hawkins, 476 S.E.2d at 807.  Any conclusion that there is an alleged correlation between HGN and a breath test result in other cases is a scientific conclusion and should be required to be scientifically accepted as having reached a “state of verifiable certainty in the scrientific community[.]”  Id. at 808.

In Hawkins, the Court further held that the “HGN test is an accepted, common procedure that has reached a state of verifiable certainty in the scrientific community and is admissible as a basis upon which an officer can determine that a driver was impaired by alcohol.”  Id. at 808.  Thus, the Hawkins Court held that the trial court was no longer required to hear expert testimony in order to introduce evidence of HGN.  Id.  In reaching its conclusion that the production of evidence to satisfy the Harper standard for admissibility was no longer required, the Court observed the following:

  1. the effect of alcohol on the eyes and inducing horizontal gaze nystagmus is recognized in The Merck Manual of Diagnosis and Therapy;
  2. the horizontal gaze nystagmus test has undergone validation studies sanctioned by the National Highway Traffic Safety Administration (Burns & Moskowitz, “Psychophysical Tests for DWI Arrest,” U.S. Department of Transportation, Rep. No. DOT-HS-802-424 (1977); Schweitz & Snyder, “Field Evaluation of a Behavioral Test Battery for DWI,” U.S. Department of Transportation, Rep. No. DOT-HS-806-475 (1983);
  3. the horizontal gaze nystagmus test has been employed by law enforcement in all 50 states;
  4. the relationship of horizontal gaze nystagmus to alcohol consumption was recognized in the premier DUI defense treatise (Erwin, Defense of Drunk Driving Cases (3rd ed. 1985), § 8.15A[3]);and
  5. “The characteristics, theory, and scientific acceptability of HGN testing in relation to DUI cases has been discussed in numerous articles and in numerous judicial opinions. See particularly, State v. Superior Court, 149 Ariz. 269, 718 P.2d 171, appendices A & B 182-184, 149 Ariz. 269, 718 P.2d 171 (1986); State v. Nagel, 30 Ohio App.3d 80, 506 N.E.2d 285 (1986); see also, e.g., Barnes, The Effects of Ethyl Alcohol on Visual Pursuit and Suppression of the Vestibulo-Ocular Reflex, 406 ACTA Otolaryngol Supp., p. 161 (Sweden 1984) (ethyl alcohol disrupted visual pursuit eye movement by increasing number of nystagmic “catch-up saccades”); Goldberg, Effects and After-Effects of Alcohol, Tranquilizers and Fatigue on Ocular Phenom- ena, Alcohol and Road Traffic, p. 123 (1963) (of different types of nystagmus, alcohol gaze nystagmus is the most easily observed); Zyo, Medico-Legal and Psychiatric Studies on the Alcoholic Intoxicated Offender, 30 Japanese J. of Legal Medicine, No. 3 (1976), p. 169 (recommends use of nystagmus test to determine somatic and mental symptoms of alcohol in- toxication, as well as blood alcohol content).”

Hawkins, 476 S.E.2d at 807-808.

While Hawkins acknowledged that HGN itself satisfies the Harper standard, there is no evidence that any attempt by the officer in this case to correlate between HGN and a breath test result in other cases  would satisy Harper as “a phenomenon that may be verified with such certainty that it is competent evidence in a court of law[.]”  Harper v. State, 249 Ga. at 525.  Accordingly, evidence regarding any alleged correlation between HGN and a breath test result in other cases should be excluded from the trial of this case until the State has adequately laid a foundation for the admission of such evidence in accordance with Harper.

Respectfully Submitted, this ___ day of ____________, 2012.

One of the most common questions I’m asked by lawyers is: how it is that I deal with the horizontal gaze nystagmus test evidence of a testimony at a motions hearing or in a trial in a Georgia DUI case? First, I believe there are several approaches/tactics that you may take at a motions hearing or in a trial. The tactics and objectives that you employ at a motions hearing challenging HGN evidence in a DUI case may be different from the tactics and strategies that we use in a jury trial for a DUI case. Second, I believe you have to have some overall understanding as to what it is the horizontal gaze nystagmus test -or HGN test- actually tells the officer, and what is it doesn’t tell the office.

Addressing HGN test in a DUI case in Georgia: HGN is not correlated to person’s ability to drive safely.

So many times, that we’re caught up, typically under Georgia law, in believing that the horizontal gaze nystagmus test can be correlated to a person’s actual driving ability, and that has never been the case. There is no validation of the HGN the test whatsoever to predict your client’s ability to drive safely.

The only thing that the horizontal gaze nystagmus test has ever been shown to do is – to some varying degree of probability –  predict a person’s blood alcohol concentration. And it’s not very good at that. If any of you have you have ever been through a field sobriety training course, you recognize that HGN is actually really difficult to see. And it certainly doesn’t affect a person’s ability to see as they’re driving. So, what I have developed with a police officers through cross examination typically, is just very simply, you can’t correlate a person’s presence of HGN in the person’s eyes to their ability to drive safely. And that is in fact the reason that we are there in a less safe case – is that they’re alleging that your client had an impaired ability to drive safely as a result of alcohol or drugs.

Committed DUI Defense Lawyers

Our firm is committed to providing the very highest level of representation for people charged with DUI. Our lawyers understand the pseudo-science behind field sobriety tests, including the walk-and-turn turn test, and we understand how to challenge these pieces of evidence. We regularly defend clients charged with DUI in the following areas: