FILED

September 29, 1997

Cecil W. Crowson

Appellate Court Clerk

IN THE SUPREME COURT OF TENNESSEE

AT NASHVILLE

FOR PUBLICATION

 Filed: September 29, 1997

KENNETH McDANIEL, )

)

Plaintiff-Appellee, ) DAVIDSON CIRCUIT

)

)

 Vs. ) HON. MARIETTA M. SHIPLEY,

) JUDGE

)

CSX TRANSPORTATION, INC., )

)

Defendant-Appellant. ) No. 01-S-01-9605-CV-00095

For Appellant: For Appellee:

Wayne L. Robbins, Jr. Van Kirk McCombs, II

Gareth S. Aden James H. Wettermark

GULLETT, SANFORD, BURGE & WETTERMARK, P.C.

 ROBINSON & MARTIN, PLLC 2300 SouthTrust Tower

Nashville, Tennessee 37219 Birmingham, Alabama 35203-3204

Edward H. Stopher

BOEHL, STOPHER & GRAVES

Suite 2300, Providian Center

400 West Market Street

Louisville, Kentucky 40202-3346

O P I N I O N

AFFIRMED. ANDERSON, C. J.
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We granted this interlocutory appeal to clarify the standards for the

admissibility of scientific evidence under Tennessee Rules of Evidence 702 and

703. 

The trial court, after a Tenn. R. Evid. 104 pretrial evidentiary hearing,

admitted into evidence the testimony of plaintiffs’ experts who relied on

epidemiological studies to prove that exposure to organic solvents caused a form

of brain damage known as toxic encephalopathy. The trial court found that this

scientific evidence would substantially assist the trier of fact and was reliable and

trustworthy.

The Court of Appeals denied an interlocutory appeal. We, however,

granted the interlocutory appeal and conclude that Tennessee Rules of Evidence

702 and 703 impose a duty upon trial courts to determine whether scientific

evidence will substantially aid the trier of fact and whether the underlying facts

and data relied on by the expert witness indicate a lack of trustworthiness. The

trial court must further determine whether the reasoning or methodology

underlying the scientific evidence is sufficiently valid and reliable, and whether it

can properly be applied to the facts at issue.

In making this determination, the trial court should focus on the principles

and methodology underlying the science, and not on the conclusions of experts. 

The trial court is not required to determine that the principles and methodology

employed are generally accepted by the scientific community. The court needs

only to determine that the principles and methodology are scientifically valid and

reliable.

When these standards are applied in this case, the scientific evidence

proffered by the plaintiffs should be admitted. Accordingly, we conclude that the
1

 The particular solvents at issue in this case are: trichloroethane, trichloroethylene,

perchlo roethylene , and m ineral spirits. 

2

 Epidemiology is the “study of the distribution and determinants of health-related states

and events in populations and the application of this study to control of health problems.” 

Reference Manual on Scientific Evidence, Federal Judicial Center, p. 174 (1994)(hereinafter

“Reference Manual”).

There are two g eneral type s of epide miolog ical studies which ar e used to test a

hypothesis: (1) cohort studies and (2) case-control studies. In a cohort study, the epidemiologist

identifies a group of individuals who have been exposed to the chemical and another group of

individuals who have not been exposed to the chemical. The epidemiologist chooses two groups

as nearly identical as possible except for exposure to the chemical. The incidence rates of

disease of the exposed and non-exposed groups over a period of time is then observed. A casecontrol study involves persons who either have the disease (cases) or do not have the disease

(controls ). The c ases a nd con trols are m atched for com parison . A determ ination is m ade as to

whethe r the individua ls in the cas e and c ontrol grou ps were expos ed to the c hem ical. 

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trial court did not abuse its discretion in denying the defendant’s motion in limine

which sought to exclude the plaintiffs’ expert testimony.

BACKGROUND

This case involves eighty-four (84) cases filed pursuant to the Federal

Employers Liability Act, 45 U.S.C. § 51, et seq., by employees of the defendant

CSX Transportation, Inc. (“CSXT”), a railroad operator, which were consolidated

for motions and case management in the Davidson County Circuit Court. Each

plaintiff alleges that he has suffered brain damage due to chronic exposure to

four (4) particular organic solvents1 while working in the CSXT mechanical shops

in Nashville, Tennessee. 

The plaintiffs intend to rely upon occupational physicians to show that

long-term, low dosage exposure to the solvents has caused a form of brain

damage known as toxic encephalopathy, which is marked by diminished shortterm memory, sleeplessness, depression and anxiety. The plaintiffs’ experts rely

upon epidemiological studies,2 which they contend established the causation

between long term exposure to solvents and damage to the central nervous

system. 
3

 After collec ting the data either using a coho rt or case -control s tudy, epidem iologists

typica lly me asure ris k us ing the con cepts of “relativ e risk ” and /or “o dds ratio.” Coh ort stu dies yield

a direct measure of the risk of brain damage according to the presence or absence of solvent

exposure. This dir ect m easure, k nown as the re lative risk, is the ra tio of th e incid ence of b rain

damage or “toxic encephalopathy’ in the exposed group divided by the rate in the nonexposed

grou p. If the relativ e risk is 1.0, then there is no a ssociatio n betwee n solv ent exposure and b rain

damage. A relative risk of 4.0 indicates that the risk of disease in the exposed group is four times

higher tha n the risk of diseas e in the une xpose d group . Reference Manual at 148. By co ntrast,

case-control studies utilize an odds ratio in calculating risk. An odds ratio is based on a

comparison of the odds of having a disease when exposed to a suspected agent and when not

expos ed. Reference Manual at 149. Relative risk and odds ratio are generally similar in most

cases . 

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CSXT sought to exclude the plaintiffs’ experts on the basis that their

testimony was without sufficient scientific support. CSXT contended that the

epidemiological studies relied on by the plaintiffs did not consistently establish a

causal connection with a relative risk or odds ratio that shows a statistically

significant degree of reliability.3 It concluded, therefore, that the proffered expert

testimony on the issue would not “substantially assist” the trier of fact, and that

the facts and data underlying the testimony shows a “lack of trustworthiness.” 

At a pretrial Tenn. R. Evid. 104 evidentiary hearing, several expert

witnesses for the plaintiff and the defendant offered their opinions concerning the

effect of long-term exposure to low doses of the organic solvents involved in this

litigation. The proof indicated that the solvents belong to a family of organic

solvents known as chlorinated hydrocarbons, while mineral spirits are generally

distilled from petroleum products. The industrial utility of the solvents lies in their

ability to dissolve grease. 

The experts agreed that there is no objective diagnostic tool, (such as an

MRI, CT Scan, or X-Ray), that will support a diagnosis of toxic encephalopathy,

and that no biological mechanism has been identified that demonstrates how

exposure to the solvents causes the damage. Moreover, while the experts

agreed that acute exposure to high concentrations of the solvents can create

dizziness, disorientation, and even unconsciousness, the allegations in this case

involve exposure below the level necessary to render a person unconscious. 
4

 Baker’s report studied among others, Hanninen (1991 & 1979); Baker (1988); ArlienSoberg (1979); Elofsson (19 80); Hane (1977); Bleeker (19 91); Bolla (1990); Parkinson (1990);

Maizlsih (1985); and Spurgeon (1992 ).

-5-

One of the plaintiffs’ experts, Dr. Edward Baker, a physician specializing in

occupational medicine with two masters degrees, one in public health and

another in epidemiology, testified that he has authored twenty-six articles and

four textbook chapters on the subject of the effects of exposure to solvents. He

began studying the effects of solvent exposure on the central nervous system

while on the faculty of Harvard University’s School of Public Health. He has

summarized epidemiological studies conducted since 1985 and has concluded

that “these cross sectional studies, viewed in the aggregate, support the view

that chronic solvent exposure causes impairment of neurobehavioral function.” 

Baker, “A Review of Recent Research on Health Effects of Human Occupational

Exposure to Organic Solvents,” Journal of Occupational Medicine, Vol. 36, No.

10 (Oct. 1994).4

 Baker testified that dose/response and degree of exposure

were critical to the causation inquiry. 

Another plaintiffs’ expert, Dr. Douglas Linz, also a physician specializing in

occupational medicine, has authored four articles on the effects of exposure to

solvents and has diagnosed patients with chronic encephalopathy. Like Baker,

he has performed and reviewed the epidemiological studies on the subject and

has concluded that “chronic low dose exposure to solvents can cause chronic

encephalopathy.” Dr. Howard Frumkin, a physician with a doctorate in public

health, has evaluated patients for solvent exposure, and has researched and

written on the effects of exposure on the central nervous system. He testified

that a sufficient degree of exposure over a sufficient amount of time can cause

toxic encephalopathy, and that the diagnosis of chronic encephalopathy from low
5

 The plaintiffs’ fourth expert, Dr. Michael Kelly, was the examining physician who

diagnosed the plaintiffs’ toxic encephalopathy. He described the “differential diagnosis” procedure

he used in this regard.

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dose exposure to solvents is generally accepted throughout the United States

and the world.5

In contrast, Dr. Philip Edelman testified on behalf of the defendant that

although dose response is critical to any toxicology study, “most” in the medical

community of toxicologists did not accept the causal connection between low

dose exposure to solvents and encephalopathy. Edelman, a physician who is

board certified in toxicology and occupational/environmental medicine, criticized

the epidemiological studies that the plaintiffs’ experts relied upon for lacking a

good dose/response relationship and for failing to control for confounding factors

such as age, intelligence, and the use of alcohol. Likewise, Dr. Joseph

McLaughlin, a Ph.D. in epidemiology, testified that the epidemiological studies on

the relation between exposure to solvents and toxic encephalopathy failed to

account for significant confounding factors. Finally, Dr. Robert James, a Ph.D. in

pharmacology, testified that he reviewed forty-five cross sectional studies and

determined that 84 percent supported the hypothesis and 16 percent did not. He

criticized the “positive” studies, however, for failing to account for the factors of

age, intelligence, experience, and alcohol consumption. In James’s opinion, the

diagnosis of toxic encephalopathy from exposure to solvents was not generally

accepted in the medical community.

After considering the testimony of the experts and analyzing the pertinent

studies, the trial court concluded that the proposed evidence was “grounded in

scientific theory,” was “generally accepted in the occupational health

community,” and was trustworthy and reliable. Although denying the defendant’s

motion to exclude the expert testimony, the trial court recognized the need to

develop a uniform and consistent body of law and granted the defendant’s
6

 Cross-sectional studies involve selection of individuals, regardless of exposure or

disease status. Subjects for such studies are chosen either at random or via probability sampling

procedures, which allows for the exam ination of the prevalence of a disease in a representative

sample of the popu lation. McCunney, “Epidemiology and Biostatics,” A Prac tical Appro ach to

Occupational and Environmental Medicine (2nd Ed.),” at 349 . Case reports are not

epidemiological studies, but merely reports of individuals who have been exposed to an agent and

then report symptoms associated with the disease. Case reports usually precede the institution

of formal epidemiological research, although they can be important in determining whether an

association exists between an agent and a disease or defect. For example, the medical

community became aware of the association between the drug, Thalidomide, used by pregnant

women as a sedative and birth defects in their children as a result of case reports.

-7-

motion for an interlocutory appeal pursuant to Tenn. R. App. P. 9. Although the

Court of Appeals denied the interlocutory appeal, we granted the appeal to clarify

the standards for determining the admissibility of scientific evidence in this

jurisdiction. We now affirm the trial court.

SCIENTIFIC LITERATURE

We begin our analysis by reviewing the relevant material that was

submitted to the trial court and discussed by several of the experts during the

evidentiary hearing. In the 1970's, researchers in certain Scandinavian

countries, performing epidemiological studies using case report and crosssectional methods,6

 reported that neuropsychiatric symptoms may be induced by

long-term exposure to solvents. In 1979, the Danish physician, Arlien-Soborg,

coined the phrase “chronic painters’ syndrome,” in a study done on seventy

house painters. The report concluded that the majority of the painters who had

been exposed to organic solvents, often through a period with acute intoxication

symptoms, had gradually developed signs of a chronic brain syndrome. The

symptoms included impaired memory, fatigue, personality change, headaches,

and irritability. Arlien-Soborg, et al., “Chronic Painters’ Syndrome - Chronic Toxic

Encephalopathy in House Painters,” Acta. Neurol. Scand, 60:149-156 (1979). 

Other authors, including plaintiffs’ expert Dr. Edward Baker, have reported that

the Scandinavian studies supported the hypothesis that toxic encephalopathy

occurs in individuals heavily exposed to solvents over a period of months to
7

 Other s tudies ref erence d by the pa rties supp orting the th eory include Axleso n, et al.,

1976; Hanninen, et al., 1976; Hane, et al., 1977; Harkonen, et al., 1977; Knave, et al., 1978;

Mikkelson, 1980; and Gregersen, et al., 1987, among others.

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years. See Baker, et al., “The Neurotoxicity of Industrial Solvents: A Review of

the Literature, “ Am. J. of Indus. Med., 8:207-217 (1985).7

As the defendant contends, the Scandinavian studies have been criticized

for failing to prove that the painters’ symptoms were related to their occupational

exposure to organic solvents and for the disappearance of evidence of

impairment in twenty re-examined workers. See Errebo-Knudsen and Olsen,

“Organic Solvents and Presenile Dementia (The Painters’ Syndrome): A Critical

Review of the Danish Literature,” The Sci. of the Total Env’t, 48:45-67(1986);

Gade et al., “Chronic Painter’s Syndrome. A Reanalysis of Psychological Test

Data in a Group of Diagnosed Cases,” Acta Neurol. Scand., 77:293-306 (1988). 

Some studies have likewise questioned the Scandinavian studies. As one

report indicates:

Studies outside Scandinavia, mainly cross-sectional clinical

studies, have not supplied convincing evidence to support the

hypothesis of solvent exposure causing irreversible brain damage

. . . . The reason for this discrepancy might lie in differences of

study design, incomparable study populations, insufficient

adjustment for confounding factors, and, perhaps most importantly,

differences in disease classification.

Rasmussen et al., “Solvent-Induced Chronic Toxic Encephalopathy,” Am. J. Of

Indust. Med., 23:779-792 (1993); see also Williamson, et al., “A Prospective

Cohort Study of the Chronic Effects of Solvent Exposure,” Environmental Res.,

62:256-271 (1993)(“cross sectional studies suffer from problems of possible

confounding by a range of unknown factors and also usually from poor estimates

of exposure.”). Moreover, other studies have reached opposite results. See,

e.g., Spurgeon, et al., “Investigation of Dose Related Neurobehavioral Effects in

Paintmakers Exposed to Low Levels of Solvents,” Occupational & Environmental
-9-

Medicine, 51:626-630 (1994)(cross sectional study of 110 paintmakers resulted

in view that “long term exposure at or below current compliance levels does not

result in damage to the central nervous system.”).

Despite the criticisms, textbooks and review articles recognize the

diagnosis of toxic encephalopathy. For example, in the chapter entitled “Organic

Solvents and Related Compounds” of the Textbook of Clinical Occupational and

Environmental Medicine, the authors state that “there is currently sufficient

support for the association of high long-term solvent exposure with long-lasting

psycho-organic symptoms to consider this a clinical reality.” Rosenstock and

Cullen, at p. 773 (1994). 

International and national governmental health organizations also have

recognized the syndrome. For example, at the World Health Organization and

Nordic Council of Ministers meeting in Copenhagen, Denmark, in June 1985, it

was stated that “[c]linical, epidemiological and experimental data indicate that

long-term occupational exposure to organic solvents may cause adverse effects

in the central and the peripheral nervous systems.” It was recommended that

further “clinical, experimental and epidemiological studies should be undertaken

to gain further insight into the reversibility of the neurotoxic effects induced by the

solvents, their health significance and the dose-effect, dose-response

relationships.” Id. at pp. 32-33.

The National Institute for Occupational Safety and Health (“NIOSH”)

“Current Intelligence Bulletin 48,“ issued on March 31, 1989, makes similar

observations and recommends that producers and users inform their customers,

that trade associations and unions warn their workers, and that protective

equipment and worker education be used to reduce worker exposure -- at least
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to concentrations specified in exposure lists of OSHA and other organizations. 

Id. at iii-iv.

Accordingly, as the trial court found, numerous epidemiological studies

support the diagnosis of toxic encephalopathy from exposure to solvents. While

other reports have criticized the epidemiological studies, the diagnosis is

recognized in textbooks and journals, as well as by national and world health

organizations. It is with this background that we now turn to the legal principles

governing the admissibility of scientific evidence. 

SCIENTIFIC EVIDENCE

Nearly 75 years ago, the test for determining the admissibility of scientific

evidence was established in the landmark federal case of Frye v. United States,

293 F. 1013 (D.C. Cir. 1923). In Frye, which involved a polygraph examination,

or lie detector, the court said that scientific evidence will be admissible only if it

has “gained general acceptance in the particular field in which it belongs.” Id. at

1014. This rule, although followed by the vast majority of federal and state

jurisdictions, including Tennessee, was often criticized for being too restrictive of

relevant evidence, particularly new or “cutting edge” scientific theory, and too

vague for uniform application. See e.g., Symposium on Science and the Rules

of Evidence, 99 F.R.D. 188 (1983)(and extensive authority discussed therein). 

The federal courts embarked on a new and less restrictive course with the

decision recently in Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579, 113

S.Ct. 2786, 125 L.Ed.2d 469 (1993), by the U. S. Supreme Court where the

Court reversed the 9th Circuit and determined that the “general acceptance” test

set forth in Frye was superseded by Fed. R. Evid. 702: 

If scientific, technical, or other specialized knowledge will assist the

trier of fact to understand the evidence or to determine a fact in

issue, a witness qualified as an expert by knowledge, skill,
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experience, training, or education, may testify thereto in the form of

an opinion or otherwise.

According to the Court, Rule 702 requires a determination as to “whether the

expert is proposing to testify regarding scientific knowledge that will assist the

trier of fact to understand or determine a fact in issue.” Daubert, 509 U.S. at

592, 113 S.Ct. at 2796. This determination requires the trial court to consider

“whether the reasoning or methodology underlying the testimony is scientifically

valid and of whether the reasoning or methodology properly can be applied to

the facts in issue.” Id. In analyzing scientific validity or reliability, the trial court

must focus on “principles and methodology, and not on the conclusions they

generate.” Id., 509 U.S. at 595, 113 S.Ct. at 2797.

A partial list of factors the Supreme Court deemed relevant to the inquiry

included whether the theory or technique has been tested, whether it has been

subject to peer review or publication, whether there is a known or potential rate

of error, and whether, as formerly required under Frye, it is generally accepted in

the relevant scientific field. Id., 509 U.S. at 593-94, 113 S.Ct. at 2796-2798. On

remand, the Ninth Circuit Court of Appeals also considered whether the expert

proposes to testify about research conducted independent of litigation or whether

the expert had formulated an opinion for the express purpose of testifying. 

Daubert v. Merrell Dow Pharmaceuticals, Inc., 43 F.3d 1311, 1317 (9th

Cir.)(“Daubert II”), cert. denied, 116 S.Ct. 189, 133 L.Ed.2d 126 (1995).

Daubert’s influence was felt in Joiner v. General Electric Co., 78 F.3d 524,

530 (11th Cir. 1996), cert. granted 117 S.Ct. 1243, 137 L.Ed.2d 325 (1997). 

There, the trial court ruled that the plaintiff could not present expert testimony

that his exposure to polychlorinated biphenyls had caused lung cancer and

granted the defendant’s motion for summary judgment. On appeal, the Eleventh

Circuit, applying Daubert, emphasized: 
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In analyzing the admissibility of expert testimony, it is important for

trial courts to keep in mind the separate functions of judge and jury,

and the intent of Daubert to loosen the strictures of Frye and make

it easier to present legitimate conflicting views of experts for the

jury’s consideration.

The court stressed the trial court’s role was a narrow one:

This gatekeeping role is simply to guard the jury from considering

as proof pure speculation presented in the guise of legitimate

scientifically-based expert opinion. It is not intended to turn judges

into jurors or surrogate scientists. Thus, the gatekeeping

responsibility of the trial courts is not to weigh or choose between

conflicting scientific opinions, or to analyze and study the science in

question in order to reach its own scientific conclusions from the

material in the field. Rather, it is to assure that expert’s opinions

are based on relevant scientific methods, processes, and data, and

not on mere speculation, and that they apply to the facts in issue.

Id. at 530 (emphasis added). After applying the Daubert inquiry and analyzing

the principles and methodology underlying the plaintiff’s scientific evidence, the

Eleventh Circuit Court of Appeals held that the trial court erred in excluding the

evidence.

Although the federal courts have decided a new and less restrictive

direction was appropriate, state courts are still wrestling with the choice between

Frye and Daubert. For example, in a case involving the exact same parties,

issues, and experts as the present case, a Florida state circuit court, applied the

Frye test, which was retained in that jurisdiction by the Florida Supreme Court,

and concluded that the epidemiological studies were inconsistent and that the

criticisms of these studies - that the plaintiffs had failed to show the evidence

was “generally accepted” in the relevant scientific community - were valid and,

therefore, ruled that the evidence was inadmissible. See Roy Lee Berry v. CSX

Transportation, Inc., No. 92-2167 (filed April 28, 1995). 

On the other hand, in a federal case involving the exact same parties,

issues, and experts as the subject case, the federal district court for the
8

 Of c ours e, sc ientific evide nce also m ust be rele vant b efore it is ad mis sible. As s tated in

Tenn. R. Evid. Rule 401, “[r]elevant evidence means evidence having any tendency to make the

existence of any fact that is of consequence to the determination of the action more probable or

less pro bable tha n it would be without the evidenc e.”

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Southern District of Georgia applied Daubert, and concluded that the evidence

was admissible. The district court found that the epidemiological studies

supported the plaintiff’s claim that exposure can cause impairment, and found

that the studies and results were scientifically valid and reliable notwithstanding

the criticisms by opposing experts and reports. The court rejected the

defendant’s claim that the plaintiffs must show causation with a relative risk or

odds ratio of 2.0 or greater. See Bob Allen, et al. v. CSX Transportation, Inc.,

(S.D. Ga., filed Sept. 10, 1996).

THE TENNESSEE STANDARD

After examining the basic legal principles governing the admissibility of

scientific evidence and the change in direction by the federal courts, we turn to

Tennessee to clarify our standard of admissibility.

In general, questions regarding the admissibility, qualifications, relevancy

and competency of expert testimony are left to the discretion of the trial court. 

State v. Ballard, 855 S.W.2d 557, 562 (Tenn. 1993). The trial court’s ruling in

this regard may only be overturned if the discretion is arbitrarily exercised or

abused. Id. The specific rules of evidence that govern the issue of admissibility

of scientific proof in Tennessee are Tenn. R. Evid. 702 and 703.8 The former

provides: 

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 witness qualified as an expert by

knowledge, skill, experience, training, or education may testify in

the form of an opinion or otherwise.

And Tenn. R. Evid. 703 states:
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The facts or data in the particular case upon which an expert bases

an opinion or inference may be those perceived by or made known

to the expert at or before the hearing. If of a type reasonably relied

upon by experts in the particular field in forming opinions or

inferences upon the subject, the facts or data need not be

admissible in evidence. The court shall disallow testimony in the

form of an opinion or inference if the underlying facts or data

indicate lack of trustworthiness.

The plaintiffs contend that the expert testimony in this case is reliable and

that it will substantially assist the jury on the issue of causation. The defendant

argues that irrespective of Frye or Daubert, there must be adherence to the strict

requirements contained in the language of the rules and also a reasonable

standard for proving causation. It contends that the plaintiffs’ scientific evidence

is unreliable and must be excluded. The defendant argues that an

epidemiological study must show a relative risk of greater than 2.0, which several

courts have said means that a disease more likely than not was caused by the

specific agent or event. See Daubert v. Merrell Dow Pharmaceuticals, Inc., 43

F.3d 1311 (9th Cir. 1995), cert. denied, 116 S.Ct. 189, 133 L.Ed.2d 126 (1995);

Deluca v. Merrell Dow Pharmaceuticals, Inc., 791 F.Supp. 1042 (D.N.J. 1992),

aff’d, 6 F.3d 778 (3rd Cir. 1993). As discussed herein, the factor is certainly

relevant but we reject the contention that it should be adopted as matter of law. 

Although the advisory comments to Rule 702 indicate that Tennessee has

followed the Frye test in analyzing the admissibility of scientific evidence, one

commentator, recognizing the similarity between Tennessee Rule 702 and

Federal Rule Evid. 702, has raised the question of whether the Frye test of

“general acceptance” should be abolished in Tennessee. N. Cohen, S.

Sheppeard, and D. Paine, Tennessee Law of Evidence, § 401.20 at 124, n. 233. 
9

 The trial judge identified four different standards used by Tennessee courts to determine

admissibility of scientific evidence: (1) “Scientifically acceptable and accurate for its purpose.” 

State v. Johnson, 717 S.W.2d 298 (Tenn. Crim. App. 1986); (2) “Four-prong threshold test

involving whether the witness is an expert; whether the subject matter is proper; whether the

subject matter conforms to a generally-accepted theory; and whether the probative value of the

witness’ testimony outweighs its prejudicial effect.” State v. Schimpf, 782 S.W.2d 186 (Tenn.

Crim. App. 1989); (3) “Frye or Tenn. R. Evid. 702 and 703 .” State v. Ha rris, 866 S.W.2d 583

(Tenn. Crim. App . 1992); and (4) “Analysis under several tests” State v. Myers, 1992 WL 297626

(Tenn. Crim. App . 1992).

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Indeed, as the trial court in this case noted, there is some evidence of a

departure from the strict adherence to the Frye test by courts in this State.9

In our view, determining the standard for the admissibility of scientific

evidence requires an analysis of the unique language found in Rules 702 and

703 of the Tennessee Rules of Evidence. For instance, Tenn. R. Evid. 702

requires that the scientific evidence “substantially assist the trier of fact,” while its

federal counterpart requires only that the evidence “assist the trier of fact.” Fed.

R. Evid. 702. This distinction indicates that the probative force of the testimony

must be stronger before it is admitted in Tennessee. See, e.g., Weinstein, Rule

702 of the Federal Rules of Evidence is Sound; It Should Not Be Amended, 138

F.R.D. 631, 636 (1991). 

Similarly, Tenn. R. Evid. 703 states that “[t]he court shall disallow

testimony in the form of an opinion or inference if the underlying facts or data

indicate lack of trustworthiness.” There is no similar restriction in the federal rule. 

Fed. R. Evid. 703. Thus, as one writer has observed, “the additional language

. . . [in the Tennessee rule] is obviously designed to encourage trial courts to

take a more active role in evaluating the reasonableness of the expert’s reliance

upon the particular basis for his or her testimony.” R. Banks, Some

Comparisons Between the New Tennessee Rules of Evidence and the Federal

Rules of Evidence, Part II, 20 Mem.S.U. L. Rev. 499, 559 (1990). In sum, even

though the facts and data need not be admissible, they must be reviewed and

found to be trustworthy by the trial court. 
-16-

Based on the foregoing analysis, we conclude that Tennessee’s adoption

of Rules 702 and 703 in 1991 as part of the Rules of Evidence supersede the

general acceptance test of Frye. In Tennessee, under the recent rules, a trial

court must determine whether the evidence will substantially assist the trier of

fact to determine a fact in issue and whether the facts and data underlying the

evidence indicate a lack of trustworthiness. The rules together necessarily

require a determination as to the scientific validity or reliability of the evidence. 

Simply put, unless the scientific evidence is valid, it will not substantially assist

the trier of fact, nor will its underlying facts and data appear to be trustworthy, but

there is no requirement in the rule that it be generally accepted.

Although we do not expressly adopt Daubert, the non-exclusive list of

factors to determine reliability are useful in applying our Rules 702 and 703. A

Tennessee trial court may consider in determining reliability: (1) whether

scientific evidence has been tested and the methodology with which it has been

tested; (2) whether the evidence has been subjected to peer review or

publication; (3) whether a potential rate of error is known; (4) whether, as

formerly required by Frye, the evidence is generally accepted in the scientific

community; and (5) whether the expert’s research in the field has been

conducted independent of litigation. 

Although the trial court must analyze the science and not merely the

qualifications, demeanor or conclusions of experts, the court need not weigh or

choose between two legitimate but conflicting scientific views. The court instead

must assure itself that the opinions are based on relevant scientific methods,

processes, and data, and not upon an expert’s mere speculation. See, e.g.,

Joiner, 78 F.3d at 530. The trial court should keep in mind that the preliminary

question under Tenn. R. Evid. 104 is one of admissibility of the evidence. Once

the evidence is admitted, it will thereafter be tested with the crucible of vigorous
-17-

cross-examination and countervailing proof. After that occurs, a defendant may,

of course, challenge the sufficiency of the evidence by moving for a directed

verdict at the appropriate times. See Tenn. R. Civ. P. 50. Yet it is important to

emphasize that the weight to be given to stated scientific theories, and the

resolution of legitimate but competing scientific views, are matters appropriately

entrusted to the trier of fact. See Joiner, 78 F.3d at 534-35 (Birch, J.,

concurring).

We recognize that the burden placed on trial courts to analyze and to

screen novel scientific evidence is a significant one. No framework exists that

provides for simple and practical application in every case; the complexity and

diversity of potential scientific evidence is simply too vast for the application of a

single test. See Developments in the Law -- Confronting the New Challenges of

Scientific Evidence, 108 Harv. L. Rev. 1481, 1513-1516 (1995). Nonetheless,

the preliminary questions must be addressed by the trial court, see, Tenn. R.

Evid. 104, and they must be addressed within the framework of rules 702 and

703. 

 APPLICATION OF STANDARD

The trial court correctly foresaw the trend away from Frye and also used

the factors set forth in Daubert as a framework for analysis. As it observed, the

scientific theory that exposure to solvents may cause toxic encephalopathy has

been tested frequently over a period of 25 years. Because no precise diagnostic

device or biological mechanism can isolate the causal factor, the relevant tests

have been epidemiological studies. The experts in this case testified at length

about the field of epidemiology and the use of cohort and case-control studies. 

The experts agreed that epidemiological studies have been used to test the

hypothesis that exposure to solvents causes encephalopathy and that numerous

studies support a causal relationship. These studies have been reviewed,
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reconstructed, published in leading journals in the field, and subjected to peer

review. Although the “positive” studies have been criticized for failing to account

for confounding factors, the diagnosis is recognized in medical textbooks and

journals as well as by several national and world health organizations. We also

observe that the research in this area, including that of several of the plaintiffs’

experts, was conducted independently of this litigation.

Accordingly, we agree with the trial court’s finding that the evidence will

substantially assist the jury to understand the evidence and to determine a fact in

issue. We also agree with the trial court’s conclusion that the methodology and

principles underlying the scientific evidence are sufficiently trustworthy and

reliable to be presented to the trier of fact. The trial court is not required to

determine whether it agrees with the evidence and should not substitute its view

for the trier of fact. It should allow the jury to consider legitimate but conflicting

views about the scientific proof. Provided the evidence is scientifically valid,

criticisms of it and opposing views may be elicited on cross examination and/or

established in the defendant’s case. That is the essence of the lawsuit.

CONCLUSION

We have concluded that the scientific evidence proffered by the plaintiffs

satisfies the requirements of Tenn. R. Evid. 702 and 703, and that the trial court

did not abuse its discretion in admitting it into evidence. The trial court’s order

denying the defendant’s motion in limine is therefore affirmed and this case is

remanded to the trial court for further proceedings. Costs of the appeal are

assessed against the defendant.

 

________________________________

E. RILEY ANDERSON, CHIEF JUSTICE
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Concur: 

Drowota, Reid, Birch and Holder, JJ.