Case Name: E.I. du PONT de NEMOURS AND COMPANY, INC., Petitioners, v. C.R. ROBINSON and Shirley Robinson, Respondents
Court: Supreme Court of Texas
Jurisdiction: Texas
Decision Date: 1995-06-15
Citations: 923 S.W.2d 549
Docket Number: No. 94-0843
Parties: E.I. du PONT de NEMOURS AND COMPANY, INC., Petitioners, v. C.R. ROBINSON and Shirley Robinson, Respondents.
Judges: in which PHILLIPS, Chief Justice, and HECHT, ENOCH and OWEN, Justices, join.
Reporter: South Western Reporter Second Series
Volume: 923
Pages: 549–568

Head Matter:
E.I. du PONT de NEMOURS AND COMPANY, INC., Petitioners, v. C.R. ROBINSON and Shirley Robinson, Respondents.
No. 94-0843.
Supreme Court of Texas.
Argued Feb. 7, 1995.
Decided June 15, 1995.
Rehearing Overruled July 8, 1996.
Michael A. Hatchell, Tyler, Pamela Stanton Baron, Austin, Larry E. Cotten, Fort Worth, David A. Lowrance, Fort Worth, for petitioners.
William W. Kilgarlin, Santa Fe, NM, Jack Sanders, Jr., Marshall, Wayne Fisher, Houston, David W. Holman, Houston, Charles D. Kennedy, Arlington, for respondents.

Opinion:
GONZALEZ, Justice,
delivered the opinion of the Court,
in which PHILLIPS, Chief Justice, and HECHT, ENOCH and OWEN, Justices, join.
In this products liability case we determine the proper standard for the admission of scientific expert testimony under Rule 702 of the Texas Rules of Civil Evidence. The trial court excluded the testimony of an expert witness upon finding his opinions not scientifically reliable. The court of appeals reversed, holding that once a proponent establishes a witness's qualifications, the weight to be given the testimony and the credibility of the witness is to be determined by the trier of fact. 888 S.W.2d 490, 492. We hold that Rule 702 requires expert testimony to be relevant and reliable. Because the proponent of the testimony in this ease failed to establish that the proffered testimony was scientifically reliable, the trial court did not abuse its discretion by excluding the expert witness. Accordingly, we reverse the judgment of the court of appeals and affirm that of the trial court.
I.
C.R. and Shirley Robinson sued E.I. du Pont de Nemours and Company (DuPont) for products liability, breach of warranty, and violations of the Texas Deceptive Trade Practices-Consumer Protection Act (DTPA). Tex.Bus. & Comm.Code § 17.41-17.63. The Robinsons asserted that the application of Benlate 50 DF, a fungicide manufactured by DuPont, which they claim was contaminated, damaged their pecan orchard.
The Robinsons' sole expert witness on causation was Dr. Carl Whitcomb. Dr. Whit-comb has a Bachelor of Science degree from Kansas State University and masters and doctorate degrees from Iowa State University in horticulture, plant ecology, and agronomy. From 1972 until 1985, Dr. Whitcomb taught and researched at Oklahoma State University. Since 1985, Dr. Whitcomb has engaged in consulting work for nurseries, greenhouses, and corporations. He has written numerous books and articles on horticultural topics. Dr. Whitcomb is also on the review board of The Journal of Environmental Horticulture, and he reviews articles proposed for publication in The American Society of Horticultural Science.
Dr. Whitcomb opined that Dupont contaminated Benlate during its manufacturing process with many things, including sulfonylurea (SU) herbicides, and that the application of contaminated Benlate damaged the Robin-sons' pecan trees. One basis for his opinion was his inspection of the Robinsons' orchard in September 1992, conducted at the request of their attorney. Dr. Whitcomb visited the orchard and conducted an inspection that lasted two and a quarter hours. He visually scanned the orchard, which consists of about two hundred trees, and viewed approximately forty to fifty trees (25%) closely. He "dug up roots" on some of the trees and took random pictures of a few trees that exemplified what he was "trying to show." At his deposition, Dr. Whitcomb conceded that there was no consistent pattern of damage to the trees. He did not conduct any soil or tissue testing, did not research relevant weather conditions, and did not test any of the Benlate used by the Robinsons, even though they had one opened box of the fungicide remaining. At the time of his deposition, Dr. Whitcomb had not visited any other pecan orchards for the purpose of investigating for Benlate damage.
On October 3, 1992, Dr. Whitcomb reported his findings to the Robinsons' attorney. He based his opinion that contaminated Ben-late damaged the Robinsons' pecan trees on a method called comparative symptomology: because the Robinsons' pecan trees exhibited symptoms common to other plants treated with allegedly contaminated Benlate under dissimilar growing conditions, Benlate, the only common factor among all the plants, caused the damage.
Another basis for Dr. Whitcomb's opinion was an experiment he conducted in 1992, at the request of an attorney in Florida who represented clients asserting claims similar to the claims asserted by the Robinsons. In this study, Dr. Whitcomb applied several different concentrations and amounts of Benlate to groups of small plants in a controlled environment designed to replicate growing conditions in Florida. He maintained one control group of plants that was not treated with Benlate. Each plant was grown under identical soil, watering, lighting, and temperature conditions. Dr. Whitcomb carefully monitored the plants and observed particular symptoms common to plants and trees treated with Benlate, such as stunted growth and abnormal leaf coloring. Based on these symptoms, Dr. Whitcomb concluded that the Benlate applied to the plants in his study must have been contaminated. Dr. William Warde, a professor of statistics at Oklahoma State University, analyzed the results of Dr. Whitcomb's study. Dr. Warde concluded that the probability of Dr. Whitcomb's results being correct was ninety-nine percent.
Another basis for Dr. Whitcomb's opinion was a laboratory analysis of ten boxes of Benlate (none of which were used by the Robinsons). The tests revealed that out of eighteen substances found in the Benlate samples, only five were common to all boxes. The tests did not reveal the presence of SU contaminants. At his deposition, Dr. Whit-comb conceded that, if present, the SU contaminants in the tested Benlate were below scientifically detectable levels, and that he did not know at what level or concentration SU herbicides would damage pecan trees. He also admitted that, if free of contamination, Benlate was a good product.
Dr. Whitcomb also based his opinion on a review of reports of other plants treated with SU herbicides and one study involving the application of Benlate to cucumber plants. Lastly, Dr. Whitcomb relied upon some internal DuPont documents which concerned other claims against the company for damages caused by allegedly contaminated Ben-late and a recall of several batches of Benlate due to contamination by the herbicide atra-zine.
After deposing Dr. Whitcomb, DuPont filed a motion to exclude his testimony, alleging among other things that his opinions were speculative and unreliable. The trial court held a pretrial hearing on DuPont's motion and found that Dr. Whitcomb's testimony:
(1) was not grounded upon careful scientific methods and procedures;
(2) was not shown to be derived by scientific methods or supported by appropriate validation;
(3) was not shown to be based on scientifically valid reasoning and methodology;
(4) was not shown to have a reliable basis in the knowledge and experience of his discipline (horticulture);
(5) was not based on theories and techniques that had been subjected to peer review and publication;
(6) was essentially subjective belief and unsupported speculation;
(7) was not based on theories and techniques that the relevant scientific community had generally accepted; and
(8) was not based on a procedure reasonably relied upon by experts in the field.
Based on these findings, the trial court excluded Dr. Whitcomb's testimony, concluding that it was not reliable and would not fairly assist the trier of fact in understanding a fact in issue in the ease.
The parties agreed to try the case to the court, with the stipulation that in the event of a reversal, it would be tried the second time to a jury. At the nonjury trial, the Robin-sons again sought to introduce Dr. Whit-comb's testimony. The trial court abided by its earlier ruling and excluded it. The Rob-insons then offered a bill of exception containing Dr. Whitcomb's testimony. The trial court granted DuPont's motion for a directed verdict. The Robinsons appealed the judgment, claiming that the trial court had abused its discretion by excluding their expert testimony.
The court of appeals reversed and remanded the case for a new trial. 888 S.W.2d at 493. The court of appeals reviewed the trial court's Rule 702 inquiry in light of the following standards:
(1) A body of scientific, technical, or other specialized knowledge must exist that is pertinent to the facts in issue;
(2) The witness must have sufficient experiential capacity in his field of expertise. This capacity encompasses knowledge, skill, experience, training, and education;
(3) The facts evaluated must be within the witness' field of specialized knowledge.
Id. at 492 (quoting Guentzel v. Toyota Motor Corp., 768 S.W.2d 890, 897 (Tex.App.— San Antonio 1989, writ denied)). The court of appeals concluded that the trial court abused its discretion by excluding the expert testimony since DuPont had not contested Dr. Whitcomb's qualifications, only the methodology and research upon which he based his opinions. Id. at 492. The court of appeals further held that the jury was to determine the weight to be given Dr. Whitcomb's testimony and his credibility as an expert witness. Id. at 493 (citing First City Bank-Farmers Branch v. Guex, 659 S.W.2d 734, 739 (Tex.App.— Dallas 1983), aff'd, 677 S.W.2d 25 (Tex.1984)).
II.
A.
As numerous courts and commentators have observed, the use of expert witnesses in litigation has become widespread. See, e.g., In re Air Crash Disaster, 795 F.2d 1230, 1234 (5th Cir.1986) (observing that "the professional expert is now commonplace"); 2 Goode et al., Guide to the Texas Rules of Evidence: Civil and CRIMINAL § 702.2, at 17 (Texas Practice, 2d ed. 1993); Richey, Pro- posáis to Eliminate the Prejudicial Effect of the Use of the Word "Expert" Under the Federal Rules of Evidence in Civil and Criminal Jury Trials, 154 F.R.D. 537, 540 (1994) (noting an increase in the use of expert witnesses and in the services available to assist attorneys in locating them); Forinash, Comment, Analyzing Scientific Evidence: From Validity to Reliability with a Two-Step Approach, 24 St. Maey's L.J. 223, 251 & n. 130 (1992) (stating that the "number of professional expert witnesses has increased" since expert testimony is "almost indispensable" in contemporary trials). In addition, the scientific theories about which these experts often testify have increased in complexity and have become more crucial to the outcome of the case. Black et al., Science and the Law in the Wake o/Daubert: A New Search for Scientific Knowledge, 72 Tex.L.Rev. 715, 801 (1994). These developments pose a difficult problem for trial judges ruling on the admissibility of an expert's testimony, which one commentator has described as follows:
In the past decade courts have faced the difficult task of ruling on the admissibility of evidence derived from a wide range of newly ascertained or applied scientific principles. Neutron activation analysis, sound spectrometry (voice prints), psycholinguistics, atomic absorption, remote electromagnetic sensing, and bite mark comparisons are but a sample of the kinds of scientific evidence inundating the courts.
Giannelli, The Admissibility of Novel Scientific Evidence: Frye v. United States, a Half-Century Later, 80 Colum.L.Rev. 1197, 1198 (1980) (footnotes omitted).
Professional expert witnesses are available to render an opinion on almost any theory, regardless of its merit. Chaulk v. Volkswagen of Am., Inc., 808 F.2d 639, 644 (7th Cir.1986) (quoting Keegan v. Minneapolis & St. Louis R.R., 76 Minn. 90, 78 N.W. 965, 966 (1899)) (observing that almost anything, no matter how absurd, can "be proved by some so-called 'experts'"). While many of these experts undoubtedly hold reliable opinions which are of invaluable assistance to the jury, there are some experts who "are more than willing to proffer opinions of dubious value for the proper fee." 2 Goode, supra, § 702.2, at 17; see Havner v. E-Z Mart Stores, Inc., 825 S.W.2d 456, 465-66 (Tex.1992) (Cornyn, J., dissenting) (noting the "corrupting influence" of the use of experts who are paid to conduct an investigation and render an opinion in a case).
Expert witnesses can have an extremely prejudicial impact on the jury, in part because of the way in which the jury perceives a witness labeled as an expert. "[T]o the jury an 'expert' is just an unbridled authority figure, and as such he or she is more believable." Richey, 154 F.R.D. at 544. A witness who has been admitted by the trial court as an expert often appears inherently more credible to the jury than does a lay witness. See id. at 545. Consequently, a jury more readily accepts the opinion of an expert witness as true simply because of his or her designation as an expert.
Added to the potentially prejudicial influence of the term expert is the difficulty inherent in evaluating scientific evidence. Jurors are often expected to understand complex testimony regarding arcane scientific concepts and are even asked to resolve issues on which the experts cannot agree. Brock v. Merrell Dow Pharmaceuticals, Inc., 874 F.2d 307, 309 (5th Cir.), modified, 884 F.2d 166 (1989), cert. denied, 494 U.S. 1046, 110 S.Ct. 1511, 108 L.Ed.2d 646 (1990). Because expert evidence can be hard to evaluate, it can be both powerful and misleading. Weinstein, Rule 702 of the Federal Rules of Evidence is Sound; It Should Not Be Amended, 138 F.R.D. 631, 632 (1991). Consequently, some commentators believe that "ostensibly scientific testimony may sway a jury even when as science it is palpably wrong." Black, supra, at 789.
In light of the increased use of expert witnesses and the likely prejudicial impact of their testimony, trial judges have a heightened responsibility to ensure that expert testimony show some indicia of reliability. See In re Air Crash Disaster, 795 F.2d at 1234 (stating that "experts whose opinions are available to the highest bidder have no place testifying in a court of law, before a jury, and with the imprimatur of the trial judge's deci sion that he is an 'expert' "). It is especially important that trial judges scrutinize proffered evidence for scientific reliability when it is based upon novel scientific theories, sometimes referred to as "junk science."
Concerns over the abusive use of the professional expert witness have led some commentators to call for the adoption of a reliability standard for Rule 702 of the Texas Rules of Civil Evidence. See, e.g., 2 Goode, supra, § 702.5, at 37-38 (urging the adoption of a reliability standard and noting that the "goal of rooting out bogus expert opinion from the Texas courts is laudable"); Sutton, Article VII: Opinions and Expert Testimony in Texas Rules of Evidence Handbook, 30 Hous.L.Rev. 797, 842 (2d ed. 1993) (stating that reliability, rather than general acceptance, is the appropriate standard for dealing with the problems related to expert testimony); cf. Pope, The Presentation of Scientific Evidence, 31 Tex.L.Rev. 794, 794 (1953) (arguing that evidence which departs from the scientific method should not be admitted).
B.
Rule 702 of the Texas Rules of Civil Evidence, which governs the admission of expert testimony, provides as follows:
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, experience, training, or education, may testify thereto in the form of an opinion or otherwise.
Since the adoption of Rule 702 in 1983, this Court has not had occasion to address the proper standard for the admission of expert testimony. (We have addressed the legal sufficiency of scientific evidence, an inquiry which is outside the scope of Rule 702. See, e.g., Duff v. Yelin, 751 S.W.2d 175, 176 (Tex. 1988).) The courts of appeals, however, have been presented with this issue and have come to differing conclusions. Some courts of appeals have limited the trial court's inquiry to assessing the expert's qualifications. E.g., Guentzel, 768 S.W.2d at 897; Vogelsang v. Reece Import Autos, Inc., 745 S.W.2d 47, 49 (Tex.App.— Dallas 1987, no writ) (holding that the trial court only makes the "threshold finding, that the witness possesses minimal qualifications as an expert"). Other courts have held that the proper inquiry for the admission of expert evidence is whether the underlying scientific principle is sufficiently rehable to be of assistance to the trier of fact. E.g., Gannett Outdoor Co. of Tex. v. Kubeczka, 710 S.W.2d 79, 89 (Tex.App.— Houston [14th Dist.] 1986, no writ); Thompson v. Mayes, 707 S.W.2d 951, 956 (Tex.App.— Eastland 1986, writ ref d n.r.e.).
We granted DuPont's application for writ of error to resolve the conflict between the courts of appeals by determining the appropriate standard for the admission of scientific expert testimony. DuPont argues that under "the court of appeals' restricted guidelines, the trial judge is not a gatekeeper but an idle spectator rendered powerless to ensure the integrity of courtroom evidence." In order to stem the flow of the use of "junk science" and "kitchen chemistry" in our courts, DuPont urges us to adopt a reliability standard similar to the standards applicable to Rules 702 of the Federal Rules of Evidence and the Texas Rules of Criminal Evidence, which are identical to Rule 702 of the Texas Rules of Civil Evidence.
C.
In Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 589-90, 113 S.Ct. 2786, 2795, 125 L.Ed.2d 469 (1993), the United States Supreme Court stated that Rule 702 of the Federal Rules of Evidence requires scientific expert testimony to be reliable and relevant. The underlying suit arose when two minor children were born with birth defects. Their parents sued Merrell Dow, alleging that the mothers' ingestion during their pregnancies of Bendectin, an anti-nausea drug manufactured and marketed by Merrell Dow, caused the birth defects. Although there were more than thirty published studies which concluded that Bendec-tin was not capable of causing birth defects in unborn babies, the plaintiffs submitted the testimony of eight experts who claimed that Bendectin was a cause of birth defects. The plaintiffs' experts based their opinions on animal studies, pharmacological studies, and a reanalysis of previously published epidemi ological studies. The district court granted Merrell Dow's motion for summary judgment because the plaintiffs failed to establish that the principle upon which their experts based their opinions was generally accepted by the relevant scientific community. Daubert v. Merrell Dow Pharmaceuticals, Inc., 727 F.Supp. 570, 572 (S.D.Cal.1989) (quoting United States v. Kilgus, 571 F.2d 508, 510 (9th Cir.1978)). The Ninth Circuit Court of Appeals affirmed, citing Frye v. United States, 293 F. 1013, 1014 (D.C.Cir.1923), which established the "general acceptance" test. Daubert v. Merrell Dow Pharmaceuticals, Inc., 951 F.2d 1128, 1131 (9th Cir.1991), vacated, 509 U.S. 579, 113 S.Ct. 2786, 125 L.Ed.2d 469 (1993).
The Supreme Court held that Rule 702 did not incorporate the Frye test, noting that Frye's restrictive "general acceptance" test was at odds with the liberal approach of the Federal Rules of Evidence. Daubert, 509 U.S. at 588, 113 S.Ct. at 2794 (quoting Beech Aircraft Corp. v. Rainey, 488 U.S. 153, 169, 109 S.Ct. 439, 450, 102 L.Ed.2d 445 (1988)). Rather, Rule 702 requires the proffered testimony to be: (1) "scientific knowledge" (2) which will "assist the trier of fact to understand the evidence or to determine a fact in issue." Id. at 589, 113 S.Ct. at 2795 (quoting Fed.R.Evid. 702). To constitute "scientific knowledge," the proffered testimony must be reliable. Id. In addition, to be helpful to the trier of fact, the evidence must be relevant. Scientific evidence is relevant when there is a "valid scientific connection to the pertinent inquiry as a precondition to admissibility." Id. at 592, 113 S.Ct. at 2796. The Court enumerated four non-exclusive factors to aid trial judges in determining whether scientific evidence is relevant and reliable and thus admissible under Federal Rule of Evidence 702: (1) whether a theory or technique can be and has been tested (falsifiability); (2) whether the theory or technique has been subjected to peer review and publication; (3) the technique's known or potential rate of error; and (4) the general acceptance of the theory or technique by the relevant scientific community. Id. at 591-94, 113 S.Ct. at 2796-97.
The Supreme Court remanded Daubert to the Ninth Circuit, directing it to determine whether the expert testimony rested "on a reliable foundation" and was relevant to the issues in the case. Id. at 597, 113 S.Ct. at 2799. Upon remand, the Ninth Circuit held the testimony regarding Bendectin's effects was inadmissible under Rule 702, in part because it was not based on a reliable methodology. Daubert v. Merrell Dow Pharmaceuticals, Inc., 43 F.3d 1311, 1322 (9th Cir. 1995) (upon remand). The court noted that two factors indicated the expert testimony was not reliable. The first factor was that the experts had conducted their research for the purpose of testifying, rather than independently of any litigation. Id. at 1317. The second factor was the lack of any peer review or publication of the research analysis supporting the experts' conclusions. Id. at 1318. The court noted that "the only review the plaintiffs' experts' work has received has been by judges and juries, and the only place their theories and studies have been published is in the pages of federal and state reporters." Id. The court further held that the evidence was not helpful to the jury, and thus was not relevant, because the experts could not say that the Bendectin had caused the plaintiffs' injuries or that it had more than doubled the likelihood of birth defects. Id. at 1322.
Since Daubert, one Texas court of appeals has adopted a combined reliability and relevancy standard for determining the admissibility of evidence offered pursuant to Rule 702 of the Texas Rules of Civil Evidence. See North Dallas Diagnostic Ctr. v. Dewber ry, 900 S.W.2d 90, 94 (Tex.App.— Dallas 1995, n.w.h.). Two courts of appeals have come to differing conclusions about whether a Daubert-type standard governs appellate reviews of the legal sufficiency of scientific expert testimony. Compare Merrell Dow Pharmaceuticals, Inc. v. Havner, 907 S.W.2d 535, 542 (Tex.App.— Corpus Christi 1994, n.w.h.) (holding that "an expert scientific opinion must be grounded, at the very least, on some demonstrable underlying scientific data or logical inferences therefrom") with Maritime Overseas Corp. v. Ellis, 886 S.W.2d 780, 787, 791-92 (Tex.App.— Houston [14th DistJ 1994, writ pending) (rejecting Daubert ⅛ "scientific methodology" approach as the controlling standard of evidence in Texas negligence cases and in suits brought under the Jones Act, 46 U.S.C.App. § 688).
The Texas Court of Criminal Appeals also has held that scientific evidence offered pursuant to Rule 702 of the Texas Rules of Criminal Evidence must be relevant and reliable. See Kelly v. State, 824 S.W.2d 568 (Tex.Crim.App.1992). In Kelly, a defendant convicted of murder appealed the trial court's ruling on the admissibility of the State's DNA "fingerprint" evidence. At trial, the defendant objected to the admission of the State's expert testimony regarding DNA identification test results, arguing that the tests were not generally accepted as reliable by the scientific community. Id. at 569. The trial court admitted the testimony over the defendant's objection. Id. at 570. The court of appeals affirmed, based on its finding that DNA evidence was scientifically reliable. Kelly v. State, 792 S.W.2d 579, 585 (Tex.App.— Fort Worth 1990,) aff'd, 824 S.W.2d 568 (Tex.Crim.App.1992). The Court of Criminal Appeals approved, holding that evidence is reliable if the underlying theory and the technique applying it are valid, and if the technique was properly applied on the occasion in question. Kelly, 824 S.W.2d at 573. Under Kelly, factors affecting the trial court's determination of reliability include: (1) general acceptance of the theory and technique by the relevant scientific community; (2) the expert's qualifications; (3) the existence of literature supporting or rejecting the theory; (4) the technique's potential rate of error; (5) the availability of other experts to test and evaluate the technique; (6) the clarity with which the theory or technique can be explained to the trial court; and (7) the experience and skill of the person who applied the technique on the occasion in question. Id. (citing 3 Weinstein & Berger, Weinstein's Evidence ¶ 702[03] (1991)).
D.
We are persuaded by the reasoning in Daubert and Kelly. Therefore, we hold that in addition to showing that an expert witness is qualified, Rule 702 also requires the proponent to show that the expert's testimony is relevant to the issues in the case and is based upon a reliable foundation. The trial court is responsible for making the preliminary determination of whether the proffered testimony meets the standards set forth today. See Tex.R.Civ.Evid. 104(a) (stating that the trial court is to decide preliminary questions concerning the admissibility of evidence).
Rule 702 contains three requirements for the admission of expert testimony: (1) the witness must be qualified; (2) the proposed testimony must be "scientific . knowledge"; and (3) the testimony must "assist the trier of fact to understand the evidence or to determine a fact in issue." Tex.R.Civ.Evid. 702. In order to constitute scientific knowledge which will assist the trier of fact, the proposed testimony must be relevant and reliable.
The requirement that the proposed testimony be relevant incorporates traditional relevancy analysis under Rules 401 and 402 of the Texas Rules of Civil Evidence. To be relevant, the proposed testimony must be "sufficiently tied to the facts of the case that it will aid the jury in resolving a factual dispute." United States v. Downing, 753 F.2d 1224, 1242 (3d Cir.1985); see Daubert, 509 U.S. at 589-93, 113 S.Ct. at 2795-96. Evidence that has no relationship to any of the issues in the case is irrelevant and does not satisfy Rule 702's requirement that the testimony be of assistance to the jury. 3 Weinstein & Berger, Weinstein's Evidence, ¶ 702[02] (1994). It is thus inadmissible under Rule 702 as well as under Rules 401 and 402.
In addition to being relevant, the underlying scientific technique or principle must be reliable. Scientific evidence which is not grounded "in the methods and procedures of science" is no more than "subjective belief or unsupported speculation." Daubert, 509 U.S. at 590, 113 S.Ct. at 2795. Unreliable evidence is of no assistance to the trier of fact and is therefore inadmissible under Rule 702. Kelly, 824 S.W.2d at 572 (quoting Kreil-ing, Scientific Evidence: Toward Providing the Lay Trier with the Comprehensible and Reliable Evidence Necessary to Meet the Goals of the Rules of Evidence, 32 Abiz. L.Rev. 915, 941-42 (1990)).
There are many factors that a trial court may consider in making the threshold determination of admissibility under Rule 702. These factors include, but are not limited to:
(1) the extent to which the theory has been or can be tested;
(2) the extent to which the technique relies upon the subjective interpretation of the expert, 3 Weinstein & BERGER, supra, ¶ 702[03];
(3) whether the theory has been subjected to peer review and/or publication;
(4) the technique's potential rate of error;
(5) whether the underlying theory or technique has been generally accepted as valid by the relevant scientific community; and
(6) the non-judicial uses which have been made of the theory or technique.
We emphasize that the factors mentioned above are non-exclusive. Trial courts may consider other factors which are helpful to determining the reliability of the scientific evidence. The factors a trial court will find helpful in determining whether the underlying theories and techniques of the proffered evidence are scientifically rehable will differ with each particular ease.
If the trial judge determines that the proffered testimony is relevant and reliable, he or she must then determine whether to exclude the evidence because its probative value is outweighed by the "danger of unfair prejudice, confusion of the issues, or misleading the jury, or by considerations of undue delay, or needless presentation of cumulative evidence." Tex.R.Civ.Evid. 403; see Daubert, 509 U.S. at 595-96, 113 S.Ct. at 2798; Kelly, 824 S.W.2d at 572; Dudley v. Humana Hosp. Corp., 817 S.W.2d 124, 127 (Tex. App.—Houston [14th Dist.] 1991, no writ).
We are confident that our trial courts will use great care when determining whether expert testimony is admissible under Rule 702. As the Supreme Court noted in Dau-bert, Rule 702 envisions a flexible inquiry focusing solely on the underlying principles and methodology, not on the conclusions they generate. 509 U.S. at 593-94, 113 S.Ct. at 2797; see Christophersen v. Allied-Signal Corp., 939 F.2d 1106, 1111 (5th Cir.1991) (en banc) (holding, in a pre-Daubert decision, that if the "expert's methodology is well founded, the nature of the expert's conclusion is generally irrelevant [to a determination of its admissibility], even if it is controversial or unique"), cert. denied, 503 U.S. 912, 112 S.Ct. 1280, 117 L.Ed.2d 506 (1992).
The dissenting opinion argues that the party objecting to the admission of the proffered evidence has the burden to prove that it is not admissible. 923 S.W.2d 549, 567. We disagree. Once the party opposing the evidence objects, the proponent bears the burden of demonstrating its admissibility. DuPont filed a motion to exclude Dr. Whit-comb's testimony, detailing with specificity the bases for its motion. At that point, the Robinsons bore the burden to establish the admissibility of the proffered evidence.
The dissenting opinion also criticizes our approach, arguing that it places a judge in "the role of amateur scientist" and that judges are not competent to assess the scientific reliability of expert testimony. Id. at 565. However, a judge does not have to be trained in science to evaluate the reliability of a theory or technique. See Black, supra at 753 (stating that, although "the details of science may be complex," "the characteristics of valid scientific knowledge and the kind of reasoning that produce it are not difficult to grasp"). Judges are capable of understanding and evaluating scientific reliability. See Faigman, To Have and Have Not: Assessing the Value of Social Science to the Law as Science and Policy, 38 EmoRY L. J. 1005,1014 (1989). In fact, there is some authority that they are better-equipped to do so than are juries. As one commentator recently noted:
Juries must depend mostly on listening to oral testimony, often mixed in with evidence about other issues. Judges, however, have the benefit of reviewing documents and briefs.... Over time, most judges will probably develop at least some facility for understanding science beyond the typical juror's level of understanding. Taking the time required to educate jurors and to present them with similarly detailed information could easily overwhelm the other issues in a case.
Black, supra, at 788 (footnotes omitted). Moreover, many lawyers hesitate to extensively cross-examine expert witnesses because it can be difficult to explain weaknesses in the testimony to the jury and can even make things worse. See id. at 789. On the other hand, judges can freely ask questions in a preliminary hearing and thus can glean more information without these risks. Id. at 790.
E.
The Robinsons contend that allowing the trial judge to assess the reliability of expert testimony violates their federal and state constitutional rights to a jury trial by infringing upon the jury's inherent authority to assess the credibility of witnesses and the weight to be given their testimony. See U.S. Const, amend. VII; Tex. Const, art. 5, § 10. We disagree. The right to a jury trial "was designed to preserve the basic institution of jury trial in only its most fundamental elements, not the great mass of procedural forms and details." Parklane Hosiery Co. v. Shore, 439 U.S. 322, 337, 99 S.Ct. 645, 654, 58 L.Ed.2d 552 (1979) (quoting Galloway v. United States, 319 U.S. 372, 392, 63 S.Ct. 1077, 1088, 87 L.Ed. 1458 (1943)). Moreover, under the standards enunciated today, the jury will continue to assess the weight and credibility of the proffered testimony.
The trial court's role is not to determine the truth or falsity of the expert's opinion. See In re Paoli R.R. Yard PCB Litig., 35 F.3d 717, 749 (3d Cir.1994), cert. denied sub nom. General Elec. Co. v. Ingram, — U.S. -, 115 S.Ct. 1253, 131 L.Ed.2d 134 (1995). Rather, the trial court's role is to make the initial determination whether the expert's opinion is relevant and whether the methods and research upon which it is based are reliable. There is a difference between the reliability of the underlying theory or technique and the credibility of the witness who proposes to testify about it. An expert witness may be very believable, but his or her conclusions may be based upon unreliable methodology. As DuPont points out, a person with a degree should not be allowed to testify that the world is flat, that the moon is made of green cheese, or that the Earth is the center of the solar system.
III.
We now determine whether the trial court abused its discretion in excluding Dr. Whitcomb's testimony. The test for abuse of discretion is whether the trial court acted without reference to any guiding rules or principles. Downer v. Aquamarine Operators, Inc., 701 S.W.2d 238, 241-42 (Tex. 1985), cert. denied, 476 U.S. 1159, 106 S.Ct. 2279, 90 L.Ed.2d 721 (1986). The test is not whether, "in the opinion of the reviewing court, the facts present an appropriate case for the trial court's action." Id. A reviewing court cannot conclude that a trial court abused its discretion if,- in the same circumstances, it would have ruled differently or if the trial court committed a mere error in judgment. Loftin v. Martin, 776 S.W.2d 145, 146 (Tex.1989); Downer, 701 S.W.2d at 242; Jones v. Strayhorn, 159 Tex. 421, 321 S.W.2d 290, 295 (1959). The decision whether to admit evidence rests within the discretion of the trial court. Ginsberg v. Fifth Court of Appeals, 686 S.W.2d 105, 108 (Tex.1985).
Applying these principles, we cannot conclude that the trial court abused its discretion by excluding Dr. Whitcomb's testimony. It was not based upon a rehable foundation. Dr. Whitcomb conducted no testing to exclude other possible causes of the damage to the Robinsons' pecan orchard, even though he admitted in his deposition that many of the symptoms could be caused by something other than contaminated Benlate. For instance, Dr. Whitcomb stated in his deposition that any number of things, including root rot, could have caused chlorosis, a yellowing of the leaves, on the Robinsons' trees. An expert who is trying to find a cause of something should carefully consider alternative causes. In re Paoli, 35 F.3d at 758-59. Dr. Whitcomb's failure to rule out other causes of the damage renders his opinion little more than speculation.
Dr. Whitcomb's testimony is also problematic because of his methodology. Scientists may form initial tentative hypotheses. However, "coming to a firm conclusion first and then doing research to support it is the antithesis of this [scientific] method." Claar v. Burlington Northern R.R., 29 F.3d 499, 502-03 (9th Cir.1994). Dr. Whitcomb's methodology is similar to that condemned by the court in Sorensen v. Shaklee Corp., 31 F.3d 638 (8th Cir.1994):
Here the hypotheses presented by the plaintiffs' experts follow no scientific principles. Those opinions reason that, because [the children] sustained birth defects (mental retardation) and their parents used Shaklee's alfalfa tablets, and because some alfalfa tablets had contained an EtO residue, the parents must have ingested the EtO residue tablets. That inference turns scientific analysis on its head. Instead of reasoning from, known facts to reach a conclusion, the experts here reasoned from an end result in order to hypothesize what needed to he known but what was not.
While it may be that this sort of reasoning could pass muster in some cases where the obvious result explains the etiology (for example, where a fractured bone accompanied by bruised outer skin and flesh demonstrate that some type of physical contact caused the injury) such reasoning cannot apply here where several possible causes could have produced one effect.
Id. at 649 (emphases added). In this case, Dr. Whitcomb had no proof that the Robin-sons' Benlate was contaminated with SU herbicides, and no knowledge as to what amount or concentration of SU herbicides would damage pecan trees. Nonetheless, he determined, without any testing to exclude other causes, that because the Robinsons applied Benlate to their trees, and the trees showed signs of damage, the Benlate must have been contaminated.
Another factor weighing against the admissibility of Dr. Whitcomb's testimony is that his research and opinions were conducted and formed for the purpose of litigation. The fact that an opinion was formed solely for the purposes of litigation does not automatically render it unreliable. However, "when an expert prepares reports and findings before being hired as a witness, that record will limit the degree to which he can tailor his testimony to serve a party's interests." Daubert, 43 F.3d at 1317 (upon remand). On the other hand, opinions formed solely for the purpose of testifying are more likely to be biased toward a particular result. Id.
Finally, the Robinsons have offered no evidence to support their claim that comparative symptomology is an appropriate and reliable method to determine chemical contamination. Dr. Whitcomb's method of comparative symptomology has not been subjected to peer review or publication. Dr. Warde found that there was a ninety-nine percent probability that Dr. Whitcomb's conclusion that Benlate damaged the plants in Dr. Whit-comb's study was correct. However, the approach we adopt today inquires whether the particular technique or methodology has been subjected to a rate of error analysis. Moreover, there is no evidence that comparative symptomology has been generally accepted by members of the relevant scientific community. Dr. Whitcomb's self-serving statements that his methodology was generally accepted and reasonably relied upon by other experts in the field are not sufficient to establish the reliability of the technique and theory underlying his opinion. Daubert, 43 F.3d at 1316 (upon remand) (stating that an "expert's bald assurance of validity is not enough"). Also not sufficient to show general acceptance of Dr. Whitcomb's theory or technique is the fact that other organizations were studying the effects of Benlate on plant life.
IV.
Because Dr. Whitcomb's testimony and opinions were not reliable, we hold that the trial court did not abuse its discretion by excluding Dr. Whitcomb's testimony. Accordingly, we reverse the judgment of the court of appeals and affirm the judgment of the trial court.
. The Frye case concerned the admissibility of the results of a systolic blood pressure deception test, a precursor to the polygraph machine. Courts derived the "general acceptance" test from the following passage in Frye:
Just when a scientific principle or discovery crosses the 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 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.
293 F. at 1014 (emphasis added).
. "That an expert testifies based on research he has conducted independent of the litigation provides important, objective proof that the research comports with the dictates of good science." Daubert, 43 F.3d at 1317 (upon remand) (citing Huber, Galileo's Revenge 206-09 (1991)).