State Variations on the Daubert Theme:



Patrick J. Hagan

Pamela Winston Bertani




California’s Background on Admissibility of Expert Testimony

            The California Supreme Court’s unanimous 1976 decision in People v. Kelly[1] examined the admissibility of expert testimony when such testimony is based upon new scientific techniques. The Kelly opinion set forth various general principles of admissibility and outlined the traditional process for determining whether proffered expert testimony based on a new scientific technique is admissible.[2]  Step one of the process requires that “the reliability of the  method must be established, usually by expert testimony.”[3]  Step two requires that a “witness furnishing [relevant] testimony must be properly qualified as an expert to” opine on the subject at hand.[4]  In addition, the proponent of the evidence “must demonstrate that correct scientific procedures were used in the particular case.”[5]

            In considering the appropriate test for assessing a new technique’s reliability, the Kelly court confirmed its allegiance to the “general acceptance” test set forth in the 1923 Frye case.[6]  In so doing, the court rejected an alternative approach for examining reliability, which would have left the question of admissibility in the trial court’s discretion.[7]  According to Frye, “while courts will go a long way in admitting expert testimony deduced from well-recognized scientific principles 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.”[8]

            In Kelly, the California Supreme Court noted various advantages of adhering to the Frye “general acceptance” standard.[9]  Among the court’s primary reasons for continuing to follow Frye were that: (1) “those most qualified to assess the general validity of a scientific method will have the determinative voice” on such issues;[10] (2) “a minimal reserve of experts” would exist to scrutinize critically each technique in a particular case;[11] (3) consensus in the scientific community would promote uniformity of decisions; and (4) Frye’s conservative nature would protect the parties in a given case.[12]  The court explained further that Frye’s more conservative approach to evaluating reliability was consistent with the need for judicial caution in this area, particularly since jurors tend to give undue “weight to ‘scientific’ evidence when presented by ‘experts’ with impressive credentials.”[13]  Moreover, once a trial court admits evidence derived from a new technique and the decision is affirmed on appeal, the decision becomes precedent controlling subsequent trials.[14]  For these reasons, the Kelly court concluded that the more cautious Frye formulation to assessing reliability was preferable to simply submitting the matter to the trial court’s discretion.[15] 




            Daubert v. Merrell Dow Pharmaceuticals, Inc.[16] involved allegations that Bendectin, a prescription antinausea drug marketed by Merrell Dow, caused birth defects in the offspring of pregnant women who ingested it. In this sweeping 1993 opinion, the United States Supreme Court flatly rejected application of Frye as the exclusive standard for determining scientific evidence admissibility and ruled that the Federal Rules of Evidence, not Frye, governed whether expert testimony is or is not admissible.[17]  According to the Court, “[although] Frye made ‘general acceptance’ the exclusive test for admitting expert scientific testimony . . . [t]hat austere standard, absent from, and incompatible with, the Federal Rules of Evidence, should not be applied in federal trials.”[18]

In diametric opposition to the Kelly/Frye “general acceptance” test, Daubert I requires that trial judges, rather than experts in the relevant field, act as “gatekeepers” by determining whether proffered expert evidence is both reliable and relevant.[19]  The high court noted that “a rigid ‘general acceptance’ requirement[, as set forth in Frye,] would be at odds with the ‘liberal thrust’ of the Federal Rules and their ‘general approach’ of relaxing the traditional barriers to ‘opinion testimony’.”[20]  Under Daubert I, proffered evidence is relevant “[i]f scientific . . . or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue .”[21]  Such evidence is reliable if a judge determines that the evidence constitutes scientific knowledge (i.e., is derived by using the scientific method).[22]  In addition to derivation by the scientific method, other indicia of reliability include whether a theory or method has been: (i) tested; (ii) peer reviewed and published; (iii) generally accepted in the scientific community; (iv) deemed to have an acceptable rate of error; and (v) subjected to standards controlling technique operation.[23]

One year after the Daubert I decision, the California Supreme Court had an opportunity to apply the objective Daubert I standards to assess the admissibility of scientific evidence in the case of People v. Leahy.[24]  However, instead of following the United States Supreme Court’s lead on this issue, the California Supreme Court opted to continue applying Kelly/Frye as its apparently exclusive test.



California Clings to Kelly/Frye

            In People v. Leahy, the California Supreme Court addressed the issue of “whether [the defendant’s] horizontal gaze nystagmus (HGN) field sobriety test results [were] admissible in the absence of a Kelly/Frye foundational” showing that the HGN test had gained general acceptance within the relevant scientific community.[25]  The court found that the HGN test was a “new scientific technique” within the scope of Kelly/Frye, and concluded that testimony relating to the test was inadmissible for failing to comply with the Kelly/Frye general acceptance standard.[26]  In reaching its conclusion, the court engaged in a fairly thorough discussion of why “Daubert affords no compelling reason for abandoning Kelly in favor of the more ‘flexible’ approach outlined in Daubert” and consequently why California courts would continue to apply Kelly/Frye.[27]

            In Leahy both the defendant and the People urged the court to retain Kelly/Frye.[28]  The defendant encouraged the court to “preserve the ‘cautious’ and ‘conservative’ approach . . . deliberately chose[n] in Kelly.”[29]  The People, represented by the Orange County District Attorney, agreed and argued that some type of standard test must exist to help trial courts minimize the admission of “junk science” in California courts.[30]  Furthermore, amici curiae briefs took the position that adopting Daubert would “ignore over forty years of precedent based upon policy considerations which have not changed[,]” and that “California should retain the Kelly rule as an important safeguard against untested and unproven scientific theories.”[31]  The court also noted what some consider as benefits of the Kelly/Frye test, such as (i) minimizing undue influence on juries, (ii) leaving scientific questions to qualified scientists; (iii) avoiding multiple suits, and (iv) promoting uniformity in decisions.[32]

On the other side of this issue, a competing amicus curiae brief criticized Kelly/Frye for being “unclear as to the proper standard for proving general acceptance by the scientific community.”[33]  Echoing this concern, another amicus brief, criticizing the general acceptance standard, asserted that Kelly/Frye: (i) “emphasizes ‘nose counting’ of the scientific community rather than focusing directly on the reliability of the challenged technique,” which results in the exclusion of demonstrably reliable evidence; (ii) is based “on an unrealistic model of a ‘relatively monolithic scientific community,’” (iii) improperly defers the legal question of admissibility exclusively to scientists; and (iv) unduly penalizes parties by “excluding relevant evidence of guilt.”[34]  Other criticisms voiced in opposition to Kelly/Frye focused on various uncertainties that have been associated with the general acceptance test.[35]  For instance, that test was cited as being uncertain regarding (i) “whether, and to what extent, it applies to expert testimony;” (ii) whether the test requires “general acceptance of the scientific technique itself,” or of the underlying principle; (iii) what constitutes the “relevant” scientific community; and (iv) “what constitutes ‘general acceptance’ (e.g., a simple majority, a consensus, or a significant minority).”[36]  The court also noted that Kelly/Frye critics primarily focus on its conservative nature, in that “the doctrine contemplates an undefined period of testing and study by a community of experts before a new scientific technique is deemed ‘generally accepted,’ [which delays] the admissibility of evidence derived from the technique.”[37]

The California Supreme Court was not persuaded by these formidable challenges to the usefulness of Kelly/Frye as a means of assessing the admissibility of scientific evidence.[38]  Consequently, the Leahy court concluded that Kelly/Frye had indeed “survived Daubert” in the state of California, and will continue to govern the admission of evidence derived from a new scientific technique.[39]



Expansion Of Daubert Principles

In the second Daubert case[40] the Ninth Circuit Court of Appeals revisited this admissibility issue and set forth yet another factor for examining the reliability of expert testimony. According to the Ninth Circuit, showing that an expert’s testimony is based on pre-litigation research is another indicator of reliability under FRE 702.[41]  Two years later the U.S. Supreme Court decided General Electric Co. v. Joiner, [42] which clarified Daubert I even further by explaining that district courts exercising their gatekeeper role under Daubert may properly assess whether an expert’s conclusions follow from the methodology employed to reach those conclusions. And most recently in Kumho Tire Co. v. Carmichael, [43] the Court again expanded Daubert’s application and emphasized that Daubert’s general holding applies not only to testimony based on “scientific” knowledge, but also to testimony based on “technical” and “other specialized” knowledge.

            Despite the United States Supreme Court’s express rejection of the general acceptance test as the exclusive standard for assessing admissibility, California courts have steadfastly continued to apply its unique Kelly/Frye when determining the admissibility of scientific evidence.  As a result, considerable controversy has emerged regarding whether California courts should, like most other states, abandon the so-called more conservative Kelly/Frye approach and embrace Daubert’s “gatekeeping” method of broadly assessing scientific evidence admissibility.  A brief look at other California cases applying Kelly/Frye suggests that continuing to apply this general acceptance test to assess scientific evidence admissibility may result in considerably more liberal, confusing and uncertain rulings when compared to cases basing admissibility on the more comprehensive Daubert principles.



Recent Kelly/Frye Applications in California

            In 1998 the California Supreme Court decided People v. Venegas, [44] which involved a defendant whose rape conviction was based primarily on incriminating DNA evidence. In its analysis, the Venegas court applied Kelly/Frye as a three-prong test.[45]  Under prong one, to establish the admissibility of evidence produced by a new scientific technique, the new technique’s reliability must be demonstrated by showing that the technique has gained general acceptance in the particular field to which it belongs.[46]  “General acceptance under Kelly[/Frye] means a consensus drawn from a typical cross-section of the relevant, qualified scientific community.”[47]  “[O]nce a trial court has admitted evidence based on a new scientific technique, and that decision is affirmed on appeal by a published appellate decision, the precedent . . . may control subsequent trials, at least until new evidence is presented that shows a change in” the scientific community’s attitude.[48]  “The second prong requires that any witness testifying on general acceptance be properly qualified as an expert on the subject.”[49]  Prong three requires “the proponent of evidence [to] demonstrate that correct scientific procedures were used in the particular case,” but does not require a showing that the procedures used have been generally accepted by the relevant scientific community.[50]  Rather, prong three inquires into whether the procedures actually used in a particular case comply with a generally accepted methodology and technique.[51]

The Court of Appeal in Venegas had reversed the defendant’s conviction for prejudicial error in admitting DNA evidence because the prosecution failed to establish general scientific acceptance of the restriction fragment length polymorphism (RFLP) methodology used by the FBI in performing its DNA analysis.[52]  The California Supreme Court affirmed reversal of the conviction, but contrary to the Court of Appeal’s finding, it ruled that the prosecution did not have to prove general acceptance of the RFLP methodology.[53]  Rather, the court reasoned that two prior published Court of Appeal opinions, People v. Axell [54] and People v. Barney,[55] previously established general scientific acceptance of the disputed methodology, which obviated the prosecution’s need to establish general acceptance again.

However, the “general acceptance” established in Axell no longer existed by the time Barney was decided.[56]  Thus, the Venegas court cited these cases as having established general acceptance despite the fact that just one year after Axell was decided, the scientific community determined that DNA matching calculations based on RFLP methodology, which matches defendant’s DNA to crime scene DNA, was no longer generally accepted.[57]  In 1992 the Barney court actually acknowledge that general acceptance of this methodology no longer existed, but nonetheless rejected the defendants’ Kelly/Frye challenges to the disputed RFLP methodology, relying primarily on the record and rationale in Axell.[58]  Amid this controversy involving the general acceptance of DNA matching methodology, the Venegas court concluded that Axell and Barney, “clearly established general scientific acceptance” of RFLP methodology under Kelly’s first prong.[59]  Although the court ultimately ruled that admitting the evidence at trial was erroneous because the evidence was based on incorrect scientific procedures, which violated Kelly/Frye prong three, Venegas upheld the general acceptance of RFLP methodology against the express opinion of the scientific community.[60] 

Moreover, in another controversial ruling, the Venegas court held that violating Kelly/Frye prong three affected the admissibility, as opposed to the weight, of the evidence.[61]  Whereas, in People v. Farmer, [62] the court found that prong three violations went to the weight of proffered evidence, not to admissibility. [63]  To reconcile this seeming contradiction, the Venegas court distinguished its ruling based on the type of evidence involved in a given case.[64]  According to the court’s reasoning, DNA evidence, such as that proffered in Venegas, is different from other forms of scientific evidence and “[u]nlike fingerprint, shoe track, bite mark, or ballistic comparisons, which jurors essentially can see for themselves, questions concerning whether a laboratory has adopted correct, scientifically accepted procedures for . . . determining a [DNA] match depend almost entirely on the technical interpretations of experts.”[65]  Consequently, the court concluded that resolving such questions, at least where DNA evidence is concerned constitutes a prerequisite to admissibility, rather than weight, under Kelly prong three.[66]

The logical and legal inconsistencies resulting from Venegas demonstrate the inherent difficulty in applying the subjective Kelly/Frye general acceptance criteria to assess admissibility instead of adopting the more objective and flexible Daubert standards.  Other California courts have admitted a wide range of somewhat controversial evidence based on evaluations under Kelly/Frye.[67]



Post-Daubert Cases May Be “More Conservative” Than Kelly/Frye

            As currently applied, cases employing the Kelly/Frye criteria for assessing the admissibility of scientific evidence appear to be fairly liberal, when compared to post Daubert/Joiner/Kumho cases, in admitting scientific evidence.  Arguably, this result is primarily because Kelly/Frye cases rely on relatively subjective criteria in assessing admissibility (i.e., general acceptance by a consensus of the relevant scientific community), whereas Daubert cases look to more concrete admissibility standards (i.e., peer review, publication, testing, acceptable rates of error in testing, and testing standards).  For instance, in Casey v. Ohio Medical Products, [68] the district court excluded an expert’s causation testimony regarding the contraction of chronic active hepatitis. According to the court, the expert’s opinion was inadmissible because the testimony (i) was based on unreliable case reports, as opposed to controlled studies, and thus failed to establish general causation; and (ii) lacked sufficient information about the plaintiff’s pathology, and therefore failed to establish specific causation.[69]




            Despite Daubert and subsequent decisions which have abandoned “general acceptance” as the exclusive criteria for examining admissibility, California courts continue to apply the ever increasingly amorphous Kelly/Frye general acceptance test in evaluating the admissibility of evidence based on new scientific techniques. Kelly/Frye’s continued vitality in California appears to be based largely on the impression that the general acceptance test is more conservative than Daubert in terms of admissibility. This, it is believed, will of necessity diminish the amount of “junk science” being admitted in California courts.  However, recent appellate decisions, practice in trial courts, and the trend to increase state court filings demonstrate that post-Daubert federal decisions are anything but liberal in admitting proffered scientific evidence.  On the contrary, federal cases applying Daubert/Joiner/Kumho principles involve much closer, and more objective, scrutiny of scientific evidence and related testimony.  Passing through pre-admissibility evidentiary filters such as scientific method derivation, peer review, and publication virtually eliminates the likelihood of admitting anything other than scientifically reliable and relevant evidence.  As reference to scientific methods and techniques become the more prevalent form of evidentiary screening, the usefulness of Daubert and its progeny should prevail as the common judicial standard for evaluating the admissibility of scientific evidence.



[1]           549 P.2d 1240 (Cal. 1976).

[2]           Id. at 1244.

[3]           Id.

[4]           Id.

[5]           Id. (emphasis added).

[6]           Frye v. United States, 293 F. 1013 (D.C. Cir. 1923).

[7]           People v. Leahy, 882 P.2d 321 (Cal. 1994).

[8]           Frye, 293 F. at 1014 (emphasis added).

[9]           Kelly, 549 P.2d at 1244.

[10]          Id. (quoting United States v. Addison, 498 F.2d 741, 743-44 (D.C. Cir. 1974)).

[11]          Id.

[12]          Id.

[13]          Id. at 1245.

[14]          Id. This concept seems to have been followed uncritically, and not necessarily rationally, see, infra section V.

[15]          Id.

[16]          509 U.S. 579 (1993) (Daubert I).

[17]          Id. at 589.

[18]          Id.

[19]          Id.

[20]          Id. at 588 (quoting Beech Aircraft Corp. v. Rainey, 488 U.S. 153, 169 (1988)).

[21]          Id. at 590.

[22]          Id.

[23]          Id. at 593-94.

[24]          882 P.2d 321 (Cal. 1994).

[25]          Id. at 323.

[26]          Id.

[27]          Id. at 324.

[28]          Id. at 328 (emphasis added). 

[29]          Id.

[30]          Id.

[31]          Id.

[32]          Id. at 329.

[33]          Id. at 328. This is the loophole.

[34]          Id. at 329.

[35]          Id.

[36]          Id.

[37]          Id. at 330.

[38]          Id. at 331.

[39]          Id.

[40]          Daubert v. Merrell Dow Pharmaceuticals, Inc., 43 F.3d 1311 (9th Cir.), cert. denied, 516 U.S. 869 (1995) (Daubert II).

[41]          Id. at 1318.  In counterpoint, the appellate court stated that an unverified process created solely in light of a litigated issue should require extraordinary scrutiny.

[42]          522 U.S. 136 (1997).

[43]          526 U.S. 137 (1999).

[44]          954 P.2d 525 (Cal. 1998).

[45]          Id. at 543.

[46]          Id.

[47]          Id. at 549 (citing People v. Leahy, 882 P.2d 321, 336 (Cal. 1994)).

[48]          Id. at 544 (citing People v. Kelly, 549 P.2d 1240, 1245 (Cal. 1976)).

[49]          Id. at 545 (emphasis added).

[50]          Id. This may be a move toward equivalence with Joiner and Kumcho.

[51]          Id.

[52]          Id. at 528.

[53]          Id.

[54]          1 Cal. Rptr.2d 411 (Ct. App. 1991).

[55]            10 Cal. Rptr.2d 731 (Ct. App. 1992).

[56]          See, R. Kennedy & J. Martin, California Expert Witness Guide § 4.17 (2d ed. 1999) (emphasis added).

[57]          People v. Venegas, 954 P.2d 525, 546 (Cal. 1998).  See also, California Expert Witness Guide, supra note 56, § 4.17.

[58]          Barney, 10 Cal. Rptr.2d at 735.

[59]          Venegas, 954 P.2d at 552.

[60]          Id.

[61]          Id. at 554.

[62]          See, People v. Farmer, 765 P.2d 940, 955 (Cal. 1989) stating that “[t]he Kelly-Frye rule tests the fundamental validity of a new scientific methodology, not the degree of professionalism with which it is applied.  Careless testing affects the weight of the evidence and not its admissibility, and must be attacked on cross-examination or by other expert testimony.” (emphasis added).  See also, California Expert Witness Guide, supra note 56, § 4.17.

[63]          People v. Venegas, 954 P.2d 525, 547 (Cal. 1998).

[64]          Id.

[65]          Id.

[66]          Id.

[67]          See, People v. Farmer, 765 P.2d 940 (Cal. 1989) (admitting footprint analysis evidence); and People v. Joehnk, 42 Cal. Rptr.2d 6 (Ct. App. 1995) (upholding defendant’s conviction, which had been based in part on HGN field sobriety test evidence, despite Leahy’s rejection of such evidence for failure to satisfy Kelly/Frye).

[68]          877 F. Supp. 1380 (N.D. Cal. 1995).  In determining causation, the trier of fact must consider both general causation (i.e., that the alleged agent can cause the plaintiff’s disease), and specific causation (i.e., that the chemical did cause the disease alleged) (emphasis added).

[69]          Casey, 877 F. Supp. 1380. See also, Cabrera v. Cordis Corp., 134 F.3d 1418 (9th Cir. 1998) (finding that absent peer reviewed articles, supporting research, or evidence derived from the scientific method, proffered testimony is properly excluded); and Schudel v. General Elec. Co., 120 F.3d 991 (9th Cir. 1997) (excluding expert testimony based on extrapolations from irrelevant and inapplicable studies).


(Authors’ bios)

            Hagan (see Fall 1999 issue, p. 86 and use same photo).

Pamela Winston Bertani is an associate in the Sacramento, California firm of Weintraub, Genshlea, Chediak, Sproul. She received her undergraduate degree from the University of California, Berkeley and her juris doctor from Arizona State University College of Law. Ms. Bertani is a member of her firm’s Intellectual Property group and her practice also includes both patent litigation and prosecution. She is a member of the Sacramento County, Solano County and San Francisco County Bar Associations and the Women Lawyers of Sacramento.