FILED

October 13, 1997

Cecil W. Crowson

Appellate Court Clerk

IN THE SUPREME COURT OF TENNESSEE

AT NASHVILLE

(HEARD AT COOKEVILLE)

STATE OF TENNESSEE, ) FOR PUBLICATION

 )

) FILED: OCTOBER 13, 1997

Appellant ) 

) DAVIDSON COUNTY

v . ) 

) HON. WALTER C. KURTZ,

CORA MURPHY, ) JUDGE

 )

 Appellee ) NO. 01-S-01-9602-CC-00035

For Appellee : For Appellant :

JEFFERSON T. DORSEY JOHN KNOX WALKUP

Assistant Public Defender Attorney General and Reporter

Nashville, TN

MICHAEL E. MOORE

Solicitor General

WILLIAM DAVID BRIDGERS

Assistant Attorney General

Nashville, TN

VICTOR S. JOHNSON, III

District Attorney General

JAMES D. SLEDGE

Assistant District Attorney

Nashville, TN

OPINION
2

COURT OF CRIMINAL APPEALS AFFIRMED BIRCH, J. 
1Tenn. Code Ann. § 55-10-401.

2Oral argument was heard in this case on October 8, 1996, in

Cookeville, Putnam County, Tennessee, as part of this Court’s

S.C.A.L.E.S. (Supreme Court Advancing Legal Education for Students)

project.

3

The Court of Criminal Appeals reversed the judgment of

the trial court that convicted Cora Murphy, the defendant, of

driving while under the influence of an intoxicant1 and remanded

the case for a new trial. We consider now the appeal of the State

of Tennessee,2 and we must determine whether testimony concerning

an Horizontal Gaze Nystagmus (“HGN”) sobriety test constitutes

“scientific, technical, or other specialized knowledge” under

Tenn. R. Evid. 702. We hold that the HGN test is a scientific

test. To be admissible at trial, such evidence must satisfy the

requirements of Tenn. R. Evid. 702 and 703 as announced in McDaniel

v. CSX Transportation, Inc., S.W.2d (Tenn 1997). Because

we are unable to determine from the record now before us whether

these admissibility requirements have been met, the judgment of the

Court of Criminal Appeals is affirmed, and we remand this case to

the trial court for a new trial.

I

Murphy was arrested and charged with driving while under

the influence of an intoxicant on May 31, 1993. At trial, the

State relied primarily on the results of an HGN sobriety test.

Michael Eby, the arresting officer, described the test he

administered to Murphy and his conclusions therefrom as follows:
4

[The HGN test] works on the

movement of the eyes, that --- what

you check for are three different

things. One, you check for smooth

movement. You have them follow an

object, either a pen, tip of a pen

or your finger, and they’re supposed

to follow with their eyes. And if

there’s nystagmus present, their

eyes will not move from side to side

smoothly; they will have jumping

movements in them.

Then you check for, at maximum

deviation, any signs of movement.

And what it is is [sic] when you get

to a 45 degree angle, their eyes

will jerk back and forth if there’s

signs of nystagmus there.

And the last one is you check

for the offset [sic, onset] of it

before 45 degrees.

. . . .

on all three points both the eyes

[Murphy] had obvious signs of

nystagmus.

Murphy was tested as she faced the flashing lights of

Eby’s patrol car. At trial, Eby acknowledged that nystagmus may be

caused by many factors other than alcohol consumption. Eby did not

conduct any other field sobriety tests, nor was Murphy’s blood or

breath later analyzed for alcohol content. Eby also testified

concerning his general observations of Murphy made during the

incident. As stated, the trial court held that the HGN test

results did not constitute scientific evidence. The Court of

Criminal Appeals reversed. 
5

II

Nystagmus is an involuntary jerking movement of the eye

either as it attempts to focus on a fixed point or as it moves to

one side. The phenomenon results from the body’s attempt to

maintain orientation and balance. State v. Cissne, 72 Wash. App.

677, 865 P.2d 564, 566 (1994). “The theory behind the [HGN] test

is that there is a strong correlation between the amount of alcohol

a person consumes and the angle of onset of the nystagmus.” State

v. Witte, 251 Kan. 313, 836 P.2d 1110, 1112 (1992)(quoting Carper

& McCamey, Gaze Nystagmus: Scientific Proof of DUI?, 77 Ill.B.J.

146, 147 (1988)). 

The effect of alcohol consumption on nystagmus may be

observed in three ways:

“Angle of Onset--the more

intoxicated a person becomes, the

sooner the jerking will occur as the

eyes move to the side.

“Maximum Deviation--the greater the

alcohol impairment the more distinct

the nystagmus is when the eyes are

as far to the side as possible.

“Smooth Pursuit--an intoxicated

person often cannot follow a slowly

moving object smoothly with his

eyes.” 2 Nichols, Drinking/Driving

Litigation §26:01, p. 159 (1992

Supp.)

Id. at 1113.

In conducting an HGN test, the subject should be

instructed to keep the head still and with one eye covered, follow
3Whitson v. State, 314 Ark. 458, 863 S.W.2d 794 (1993); State

v. Murphy, 451 N.W.2d 154 (Iowa 1990); State v. Garris, 603 So.2d

277 (La. App. 2 Cir. 1992); City of Fargo v. McLaughlin, 512 N.W.2d

700 (N.D. 1994); State v. Nagel, 30 Ohio App.3d 80, 506 N.E.2d 285

(1986); State v. Sullivan, 426 S.E.2d 766 (S.C. 1993).

4In State v. Gilbert, 751 S.W.2d 454, 459 (Tenn. Crim. App.

1988), the Court of Criminal Appeals held that field sobriety tests

were not “scientific” and therefore, not subject to Tenn. R. Evid.

702. However, the intermediate court did not specify which field

sobriety tests were utilized in that case. There are several

unpublished opinions by the Court of Criminal Appeals that have

held that HGN test results are not scientific in nature. As author

of this opinion, I acknowledge that I participated in several of

those opinions while on the lower court and even authored one.

After further reflection, however, I have concluded that the course

we adopt today is the better-reasoned one.

6

a penlight or other object with the uncovered eye. The penlight is

held at eye level about 12 to 15 inches from the subject’s head.

It is then moved from directly in front of the subject’s eyes to

one side. As a person who has been consuming alcohol attempts to

follow the penlight’s movement, so the theory goes, nystagmus will

occur sooner and be more pronounced than it would be in a person

who has not consumed any alcohol.

The State argues, and certain other jurisdictions have

accepted this reasoning,3 that HGN testing is not scientific

because it simply involves an officer’s objective observations of

the subject’s physical characteristics. In this way, says the

State, HGN is no different from other field sobriety tests.4 

In our view, the HGN test does differ fundamentally from

other field sobriety tests because the witness must necessarily

explain the underlying scientific basis of the test in order for

the testimony to be meaningful to a jury. Other tests, in marked

contrast, carry no such requirement. For example, if a police
7

officer testifies that the defendant was unable to walk a straight

line or stand on one foot or count backwards, a jury needs no

further explanation of why such testimony is relevant to or

probative on the issue of the defendant’s condition. A juror can

rely upon his or her personal experience or otherwise obtained

knowledge of the effects of alcohol upon one’s motor and mental

skills to evaluate and weigh the officer’s testimony. However, if

a police officer testifies that the defendant exhibited nystagmus,

that testimony has no significance to the average juror without an

additional explanation of the scientific correlation between

alcohol consumption and nystagmus. In effect, the juror must rely

upon the specialized knowledge of the testifying witness and likely

has no independent knowledge with which to evaluate the witness’s

testimony. 

And there is another distinction between the HGN test and

other field sobriety tests, and it concerns measurement. Returning

to examples, an officer may testify that the subject performed the

“finger to nose” test successfully three out of seven attempts.

Once again, no explanation is needed. In contrast, when an officer

testifies that the subject’s eye movement was rapid and very jerky

at less than a 40 degree angle, that officer is testifying about a

measurement that probably should be taken with a measuring device.

Therefore, the accuracy of this testimony may be questionable in

light of the officer’s non-scientific measurement of a

scientifically measurable phenomenon.
8

In Witte, the Kansas Supreme Court cogently summarized

the distinction between the HGN test and other field sobriety

tests:

The HGN test is distinguished from

other field sobriety tests in that

science, rather than common

knowledge, provides the legitimacy

for HGN testing. . . . HGN test

results are “scientific evidence

based on the scientific principle

that consumption of alcohol causes

the type of nystagmus measured by

the HGN test.” . . .

[T]he officer’s opinion that the

defendant “was under the influence

of alcohol, to the extent it was

based on the nystagmus test, rests

on scientific premises well beyond

[the officer’s] knowledge, training,

or education. Without some

understanding of the processes by

which alcohol ingestion produces

nystagmus, how strong the

correlation is, how other possible

causes might be masked, what margin

of error has been shown in

statistical surveys, and a host of

other relevant factors, [the

officer’s] opinion on causation,

notwithstanding his ability to

recognize the symptom, was

unfounded.”

Witte, 836 P.2d at 1115-16 (quoting Commonwealth v. Miller, 367 Pa.

Super. 359, 365, 532 A.2d 1186 (1987) and People v. Williams, 3

Cal. App. 4th 1326, 1334, 5 Cal. Rptr. 2d 130 (1992)). 

Tennessee Rule of Evidence 702 states:

If scientific, technical, or other

specialized knowledge will

substantially assist the trier of

fact to understand the evidence or

to determine a fact in issue, a
5Tennessee Rule of Evidence 702 requires that the evidence

“substantially” assist the trier of fact; in contrast, the federal

rule simply requires that the evidence assist the trier of fact.

6An apparent majority of the jurisdictions that have addressed

this issue agree with our conclusion. See State v. Merritt, 36

Conn. App. 76, 647 A.2d 1021, 1026 (1994) and the authorities cited

therein.

9

witness qualified as an expert by

knowledge, skill, experience,

training, or education may testify

in the form of an opinion or

otherwise.5

In Tennessee, evidence constitutes “scientific, technical, or other

specialized knowledge” if it concerns a matter that “the average

juror would not know, as a matter of course. . . .” State v.

Bolin, 922 S.W.2d 870, 874 (Tenn. 1996). In our view, the average

juror would not know, as a matter of course, that a correlation

exists between alcohol consumption and nystagmus. Consequently,

testimony concerning the HGN field sobriety test constitutes

“scientific, technical, or other specialized knowledge.”6 As such,

it must be offered through an expert witness and must meet the

requirements of Tenn. R. Evid. 702 and 703 as explained in McDaniel

v. CSX Transportation, S.W.2d (Tenn 1997).

The judgment of the Court of Criminal Appeals is

affirmed, and the cause is remanded to the trial court for a new

trial. Costs are taxed to the State for which execution may issue,

if necessary.

________________________________________

ADOLPHO A. BIRCH, JR., Justice

CONCUR:

Anderson, C.J.

Drowota, Reid, JJ.

O’Brien, S.J.