Author: Stephen P. Hurley
Co-author: Marcus J. Berghahn

Because expert testimony is a particularly effective manner of presenting evidence and because the use of an expert may reinforce, with objective data and experience, what had previously been subjective or equivocal facts, the admissibility of expert testimony is often a critical pretrial battle for defense counsel.

The Wisconsin rules of evidence provide for the liberal admission of expert testimony 2 of hard and soft sciences. 3 In contrast to the federal rule, Wisconsin courts have held that the admissibility of expert evidence lies in the relevance of the expert’s testimony, once qualified. 4 An evaluation of Wisconsin case law reveals that often the analysis performed by Wisconsin courts in considering the admissibility of expert testimony follows the standard of the federal rule. Nonetheless, the mere mention of the federal rule in state court will, generally, cause the court to rule against you. The practice of evaluating an expert’s testimony according to the federal rule’s analysis of Daubert 5 permits counsel the best opportunity to exclude the other party’s expert testimony, particularly where the state seeks the admission of expert testimony in a “soft” science. 6 The factors set forth in Daubert provide counsel with an outline with future earnings); State v. Richardson, 189 Wis.2d 418, 525 N.W.2d 378 (Ct.App. 1994)(admission of expert testimony on battered woman’s syndrome and “cycle of violence”); State v. Bednarz, 179 Wis.2d 460, 507 N.W.2d 168 (Ct.App. 1993)(admission of expert testimony on battered woman’s syndrome); Dang Vang v. Vang Xiong X. Toyed, 944 F.2d 476 (9th Cir.1991)(expert testimony on Hmong culture and unique cultural differences); State v. Hamm, 146 Wis. 2d 130, 430 N.W.2d 584 (Ct.App. 1988)(expert testimony concerning eye witness identification); State v. Hampton, 92 Wis. 2d 450, 285 N.W.2d 868 (1979)(expert testimony concerning eye witness identification); State v. Johnson, 118 Wis. 2d 472, 348 N.W.2d 196(Ct.App. 1984 )(expert testimony concerning eye witness identification); State v. Stinson, 134 Wis. 2d 224, 397 N.W.2d 126 (Ct.App. 1986)(admission of fingernail comparison evidence); John BBB Doe v. Archdiocese of Milwaukee, 211 Wis.2d 312, 565 N.W.2d 94 (1997)(expert testimony on repressed memory); State v. Lujan (Arizona), 64 Cr.L.Rep. 101 (11-11-98)(hypersensitivity to contact as defense to sexual contact).

Courts have historically applied three approaches to determine whether expert testimony ought be found admissible: the general acceptance test; the court as gate-keeper; and the relevancy test. While these three tests differ superficially, the analysis required for each test is relatively similar and use of these three tests in state court will permit counsel to best challenge or underscore the admissibility of scientific expert testimony. Counsellor beware, however, as mere mention of the Frye and/or Daubert in an argument concerning expert testimony will likely be followed by a rebuke that Wisconsin has rejected the first and not yet subscribed to the second. Using the elements of the test, however, will permit the court, if convinced, to rule in favor of the counsel who makes the argument.

The Frye test 7 articulated that, in order to be admissible, evidence upon which the underlying scientific principle is based must have “gained general acceptance in the particular field to which it belongs.” 8 If the trial court determines that the scientific principle is generally accepted in the scientific community, then the evidence is deemed sufficiently reliable to be admitted at trial. This test was subsequently adopted by some states. In light of Daubert, some states have abandoned the Frye standard while other have retained it. Many of the states which adopted the Daubert test were critical of the fact that Frye seemed to permit the introduction of “old science.”

The Frye decision was reexamined by Daubert v. Merrell Dow Pharmaceuticals, 9 in which the Supreme Court held that the Frye test was superseded by Fed.R.Evid. 702. 10 Daubert represents a departure from Frye’s general acceptance test. The Daubert court, however, noted that the reliability of the particular scientific evidence was still a consideration for admissibility. 11 In Daubert, the Court held that “the subject of the experts testimony must be “scientific … knowledge”. The adjective “scientific” implies a grounding in the methods and procedures of science. Similarly, the word “knowledge” connotes more than subjective belief or unsupported speculation.” 12 Testimony under Daubert must also satisfy additional tests must demonstrate that the expert testimony is based upon methodology that generates hypotheses and tests them to see if they can be falsified. The theory or techniques must have been exposed to peer review and publication, since “submission to the scientific community is a component to good science.” 13 Additionally, the court ought consider the rate of error or potential rate of error and the existence and maintenance of standards controlling the techniques’ operation. Finally, “general acceptance” may have bearing upon the inquiry, as widespread acceptance can be an important factor in ruling particular evidence admissible. The inquiry thus envisioned is a flexible one and the factors to be considered by the courts are not definitive. Thus the judge must ensure that any and all scientific evidence admitted, is not only relevant, but also reliable. This analysis focuses upon Fed.R.Evid. 702, and requires the judge to act as a gatekeeper. 14 If the trial court does not conclude that the scientific evidence is both relevant and reliable, the evidence may not be admitted. 15 Thus, under Frye and Daubert, reliability is a necessary precondition to the admission of scientific evidence. 16

Wisconsin, like Daubert, has rejected the Frye test in favor of a test which principally examines relevance of the proffered scientific evidence. 17 Scientific evidence may be admissible if (1) the evidence is relevant pursuant to Wis. Stats. § 904.01; 18 (2) the witness is qualified as an expert pursuant to Wis. Stats. § 907.02; 19 and (3) the evidence will assist the trier of fact. 20 If these three requirements are satisfied, the evidence may be admitted. Thus, as a general rule, scientific evidence is admissible under the relevancy test, under Wis. Stats. § 904.03, regardless of the scientific principle underlying the evidence in contrast to Daubert’s close analysis of Fed.R.Evid. 702.21

In Walstad,22 the accused was convicted of DUI after a failed suppression of evidence (after four day evidentiary suppression hearing). The supreme court held that a used breathalyzer test ampoule was not material evidence of defendant’s guilt or innocence, as the ampoule could not have been retested or reexamined in a manner that would provide relevant evidence either in respect to accuracy of original test or to guilt or innocence of defendant. Importantly, with respect to expert testimony, the court noted that the admissibility of an expert’s testimony was based upon the witness’ qualification to render the expert opinion and not the underlying theory on which the testimony is based. Thus, once qualified as an expert, the testimony is relevant and whether the witness ought be believed is a question of credibility for the finder of fact and not of admissibility.23 24

Walstad’s seeming blanket ruling that any relevant evidence, by a qualified expert witness, is admissible has been tacitly limited by the Court’s recognition that expert testimony, even if relevant, may be excluded following consideration of the factors of Wis. Stats. § 904.03 and, inter alia, if it is not based upon scientific knowledge. 25 This is the same conclusion as the Court in Daubert reached. In State v. Flattum, 26 the supreme court concluded that in the guilt phase of the trial psychiatric testimony regarding a defendant’s capacity to form intent is inadmissible for lack of reliability. Flattum, however, relied on Steele v. State27 in arriving at this conclusion. In Steele, the Wisconsin Supreme Court concluded that expert psychiatric testimony regarding a defendant’s ability to form intent was not admissible because the state of psychiatric science was not sufficiently advanced to make this determination. 28 Thus, while the holding in Steele was ultimately grounded on a reliability determination, the court’s holding was based upon a public policy determination that this type of psychiatric evidence, like polygraph examinations, 29 is not a suitable area for expert testimony. Accordingly, in Peters, 30 the court did not construe Flattum to require trial courts to make the type of ad hoc reliability determination envisioned by Daubert v. Merrell Dow Pharmaceuticals. Rather, when read in conjunction with Flattum, the decision indicates that Wisconsin courts are, indeed, concerned with the reliability of the expert evidence which they evaluate.

Despite a rule which appears to read to the contrary, Wisconsin judges do serve a limited and indirect gate keeping role when reviewing the admissibility of scientific evidence. 31 In Peters, the Court of Appeals noted that this role is much more oblique and does not involve a direct determination as to the reliability of the scientific principle on which the evidence is based. For instance, in addition to the statutory requirements, Wisconsin judges may reject relevant evidence if they conclude: (1) the evidence is superfluous, Walstad, 119 Wis.2d at 516, 351 N.W.2d at 486; (2) the evidence will involve a waste of judicial time and resources, id.; (3) the probative value of the evidence is outweighed by its prejudice to the defendant, § 904.03, Stats; (4) the jury is able to draw its own conclusions without it, Valiga v. National Food Co., 58 Wis.2d 232, 251, 206 N.W.2d 377, 388 (1973); (5) the evidence is inherently improbable, Peterson v. Peterson, 126 Wis.2d 264, 266, 376 N.W.2d 88, 89 (Ct.App.1985); or (6) the area of testimony is not suitable for expert opinion, State v. Flattum, 122 Wis.2d 282, 289 90, 361 N.W.2d 705, 709 10 (1985). The foregoing list is not an exhaustive inventory of those grounds upon which the trial court may rely in refusing to admit relevant evidence. However, it demonstrates that although Wisconsin judges do not evaluate the reliability of scientific evidence, they may restrict the admissibility of such evidence through their limited gatekeeping functions.

Peters, 192 Wis. 2d at 689, 534 N.W.2d at 873(emphasis added).

Similarly, Judge Ralph Adam Fine in State v. Blair 32 noted that the admissibility analysis, in practice, is more complicated than a mere relevance analysis, 33 especially when the proffered evidence is based on or reflects premises, theories, or hypotheses about which knowledgeable and responsible persons might reasonably differ, that is, “evidence whose scientific fundaments are not suitable candidates for judicial notice,” the threshold question of whether the expert testimony should be admitted is complex and the trial court’s analysis under Rule 907.02, Stats., must be searching.

Blair, 164 Wis. 2d 64, 473 N.W.2d 566, 572 n.9 (Ct.App. 1991)(internal citations omitted).

In the Blair decision, Judge Fine points to United States v. Downing,34 as an example of the analysis each court ought undertake with respect to the admissibility of expert testimony. The Downing court identified three areas of inquiry: (1) whether there exists a proper foundation for the expert’s testimony; (2) whether the expert’s testimony will overwhelm, confuse of mislead the jury; and (3) whether and to what extent the proffered evidence is relevant to a disputed fact. 35

The sufficiency of the foundation antecedent to the expert’s testimony requires a two-step analysis. First the court must examine whether the data upon which the expert has relied is either of a type reasonably relied upon by experts in the particular field or whether the data is properly before the jury. The second aspect of the examination of the expert’s foundation is more complicated: it requires that the court ascertain whether the data underlying the expert’s opinion is valid and if so, whether the expert’s analysis of that data is also valid.36

Whether or not the scientific principles involved have been generally accepted by experts in the field may still have a bearing on reliability and consequent probative value of the evidence. The expert’s qualifications and stature, the use which has been made of the new technique, the potential rate of error, the existence of specialized literature, and the novelty of the new invention, may all enter into the court’s assessment. Opinions which are based in large measure on a subjective analysis may have less probative value because it may be difficult to evaluate the skill of the expert in extrapolating a judgment from the scientific data.

Blair, 164 Wis. 2d 64, 473 N.W.2d 566,572 n.9 (Ct.App. 1991), citing 3 J. Weinstein & M. Berger, Weinstein’s Evidence 702-41 to 702-42. Thus, in the second aspect of the inquiry the court ought examine whether the principles are reliable an consequently possess any probative value to the issue of fact. In combination, this two step analysis permits the Court to ascertain whether the putative expert witness possess scientific knowledge.

The second area of inquiry is an analysis under Wis. Stats. § 904.03 and examine whether the proffered evidence will overwhelm, confuse or mislead the jury. In this regard, Downing warns that “the trial court must be wary when the proffered expert testimony carries an undeserved aura of ‘mythic infallibility.'” 37 In practice, this may be found to be especially true when the state seeks to present expert testimony on such topics as psychological profile evidence for sex offenders 38 or concerning a “cycle of violence.” 39

The third inquiry questions whether and to what extent the evidence is relevant to a disputed fact and is consistent with the generally accepted holding of Walstad. Nonetheless, counsel seeking to prevent the admission of expert testimony must undertake to demonstrate that the proffered testimony is not relevant to the issue of fact before the jury.

The lessons of Daubert, Downing, Blair and Peters are that the bases for an expert’s testimony under Daubert are tools for counsel with which one may either underscore or undermine proffered expert witness testimony. While in Daubert, the court acts as the gate-keeper, it is counsel’s duty, under Walstad, to demonstrate that the witness is not competent to testify as an expert. And if the expert is not competent to provide expert opinions, the impact of the expert’s lay witness testimony shall, if he may testify at all, be greatly diminished.

With the six points of Peters in mind, 41 counsel should undertake to (cross) examine any putative expert witness in order to develop whether the expert’s testimony is reliable and whether the underlying data is correct in light of the questions presented by each individual fact situation. The examination (or preparation) of the expert should include questions concerning the qualifications of the expert, the relevance of the testimony and in what manner the testimony will assist the jury, rather than confuse or mislead them.

An examination of the putative expert witness ought begin with questions which specifically address the Daubert factors: the known or potential error rate of method; the standard controlling techniques of method used. And whether, within the scientific community, there is general acceptance of methodology employed. 42 Where the technique or methodology is controversial, questions ought focus the court upon the notion that the testimony is based on “evidence whose scientific fundaments are not suitable candidates for judicial notice.” 43 These questions focus the court upon the question of whether the expert witness possess scientific knowledge; and such focus the jury upon the credibility and reliability of such testimony. If, the testimony does not pertain to scientific knowledge, then it may be possible to foreclose the use of the expert’s testimony. One must be cognizant in this line of questioning that while the witness may possess certain credentials which may be impressive, their expertise must be scientific in nature. Thus it is not be permissible for a respected psychologist to assess the competence of an individual accused of a crime. Such an exercise requires expertise in psychiatry. Similarly, in a case where testimony concerning “rape trauma syndrome,” it is wise to inquire into the qualification of the expert to assess such a syndrome. Certainly, as “rape trauma syndrome” is more widely recognized as post traumatic stress disorder, it is questionable whether anyone except a psychiatrist is competent to discuss such syndromes and whether the signs of the syndrome are present in the case at trial.44

Additional topics for examination should include any mix of the following: Questions on the witness’ education, certifications, licensure and the number of times expert has previously testified as an expert. Questions should also probe what certifications, licenses, etc. the expert does not hold. Additional questions, should focus upon the reliability of the evidence and ought inquire into any publications by the expert on subject matter of testimony, the names of publications of others on subject matter which are universally recognized, the names of authoritative publications upon which expert relies, the names of authoritative individuals who are recognized as reliable concerning the subject matter of your opinions in this case. Information should also be collected concerning whether the expert has ever lectured on the topic of the testimony. Moreover, the examination should focus upon any and all (or the lack of) scientific methods which were used by the expert in order to reach an opinion; the methodology must be explained as well as how the method has been tested and the extent and type of peer review which the methodology has undergone.

While in Wisconsin, questions concerning the admissibility of expert witness testimony do not explicitly inquire into numerous factors considered in federal courts, counsel should use the analysis found in Daubert and numerous other cases in order to frame their objections (or their proffer for the admission of) to expert witness testimony. Seeing Daubert as an equivalent to Walstad will empower counsel to underscore or undermine “soft” science expert testimony in a manner which will find resonance if not with the trial court, then with the court of appeals.