Opinion ID: 2262050
Heading Depth: 2
Heading Rank: 4

Heading: The Prosecution's Statistical Calculations and the Controversy Among Scientists.

Text: In the trial court, the prosecution elected to put all of its eggs in a single basket. It contended below, and maintains on appeal, that there was general acceptance in the relevant scientific community, within the meaning of Frye, of the statistical methodology by which the possibility of a random match was calculated as being one in thirty million. The trial judge rejected this contention, noting the existence of a substantial controversy among distinguished scientists as to the soundness of certain assumptions on which this calculation was predicated. Porter, 120 Daily Wash.L.Rptr. at 505-06. We agree with the trial judge's analysis, which has been further reinforced by subsequent events. In the very recent case of People v. Barney, et al., 8 Cal.App. 4th 798, 10 Cal. Rptr.2d 731 (1st Dist.1992), the California prosecutor presented essentially the same arguments as the government is making here. The court was not persuaded. We quote at length from Judge Chin's lucid analysis for the unanimous court in Barney: There is currently a fundamental disagreement among population geneticists concerning the determination of the statistical significance of a match of DNA patterns. The dispute was recently featured in a leading scientific journal, Science, in which Richard C. Lewontin of Harvard University and Daniel L. Hartl of Washington University attack the reliability of DNA statistical analysis, while Ranajit Chakraborty of the University of Texas and Kenneth K. Kidd of Yale University defend it. (Lewontin & Hartl, Population Genetics in Forensic DNA Typing (Dec. 20, 1991) Science, at p. 1745 (hereafter Lewontin & Hartl) Chakraborty & Kidd, The Utility of DNA Typing in Forensic Work (Dec. 20, 1991), Science, at p. 1735 (hereafter Chakraborty & Kidd)). Lewontin and Hartl question the reliability of the current method of multiplying together the frequencies with which each band representative of a DNA fragment appears in a broad data base. The problem, they say, is that this method is based on incorrect assumptions that (1) members of the racial groups represented by the broad data bases  Caucasians, Blacks, and Hispanics  mate within their groups at random, i.e., without regard to religion, ethnicity, and geography, and (2) the DNA fragments identified by DNA processing behave independently and thus are independent in a statistical sense  i.e., in the language of population genetics, they are in `linkage equilibrium.' (Lewontin & Hartl, supra, at p. 1746.) Lewontin and Hartl claim that, contrary to the assumption of random mating, ethnic subgroups within each data base tend to mate endogamously (i.e., within a specific subgroup) with persons of like religions or ethnicity or who live within close geographical distance. Such endogamous mating tends to maintain genetic differences between subgroups  or substructuring  which existed when ancestral populations emigrated to the United States and has not yet had sufficient time to dissipate. As a result, the subgroups may have substantial differences in the frequency of a given DNA fragment  or VNTR allele  identified in the processing step of DNA analysis. A given VNTR allele may be relatively common in some subgroups but not in the broader data base. (Lewontin & Hartl, supra, at pp. 1747-1749.)       Lewontin and Hartl conclude that because the frequency of a given VNTR allele may differ among subgroups, reference to a broad data base may produce an inaccurate frequency estimate for a defendant's subgroup. The current multiplication method may greatly magnify the error. The resulting probability for the defendant's entire DNA pattern may be in error by two or more orders of magnitude (e.g., 1 in 7.8 million could really be 1 in 78,000). (Lewontin & Hartl, supra, at p. 1749.) Chakraborty and Kidd strongly disagree. They contend that Lewontin and Hartl exaggerate both the extent of endogamy in contemporary America and the effect of substructuring on the reliability of DNA statistical analysis. They concede there is substructuring (and thus variance of VNTR allele frequencies) within the data bases but assert its effect on the reliability of frequency estimates is trivial and cannot be detected in practice. (Chakraborty & Kidd, supra, at pp. 1736-1738.) In an article introducing the Lewontin-Hartl and Chakroborty-Kidd articles, Science describes Lewontin and Hartl as two of the leading lights of population genetics who have the support of numerous colleagues. (Roberts, Fight Erupts Over DNA Fingerprinting (Dec. 20, 1991) (Science, at p. 1721 (hereafter Fight Erupts )). A population geneticist at the University of California at Irvine is said to agree that the current statistical methods could result in `tremendous' errors and should not be used without more empirical data. ( Id. at p. 1723.) The introductory article describes the debate as bitter and raging, stating that tempers are flaring, charges and countercharges are flying.... [] Dispassionate observers, who are few and far between, say that the technical arguments on both sides have merit.... [T]he debate is not about right and wrong but about different standards of proof, with the purists on one side demanding scientific accuracy and the technologists on the other saying approximations are good enough. ( Id., at p. 1721.) Science concludes that the Lewontin-Hartl and Chakroborty-Kidd articles seem likely to reinforce the notion that the [scientific] community is indeed divided under the Frye standard, although the issue may become moot within a few years with the expected introduction of even more powerful DNA techniques.... ( Id. at p. 1723.) The NRC report, which was released four months after the Science articles, acknowledges there is a [s]ubstantial controversy concerning the present method of statistical analysis. (NRC rep., supra, at p. 74.) The report does not, however, choose sides in the debate, but instead assume[s] for the sake of discussion that population substructure may exist.... (NRC rep., supra, at pp. 12, 80; see also id. at p. 94.)       Evidently, Lewontin and Hartl  along with their colleagues who agree with them,  are significant in both `number' and `expertise.' [Citation omitted.] Science describes Lewontin and Hartl as two of the leading lights of population genetics who have the support of numerous colleagues, and quotes a third population geneticist (Francisco Ayala) who agrees with the above criticism. ( Fight Erupts, supra, at p. 1721.) Lewontin has been described by one of his colleagues as `probably regarded as the most important intellectual force in population genetics alive.' ( U.S. v. Yee (N.D.Ohio 1991) 134 F.R.D. 161, 181.) Similar criticism of the statistical calculation process of DNA analysis have been leveled by other scientists in previous publications, some of which were admitted in evidence below (e.g., Lander, DNA Fingerprinting on Trial (June 15, 1989) Nature, at pp. 501, 504; Cohen, DNA Fingerprinting for Forensic Identification: Potential Effects on Data Interpretation of Subpopulation Heterogeneity and Band Number Variability (1990) 45 Am.J.Hum.Genetics 358, 367).       [T]he point is not whether there are more supporters than detractors, [13] or whether (as the Attorney General and amicus curiae claim) the supporters are right and the detractors are wrong. [14] The point is that there is disagreement between two groups, each significant in both number and expertise (a [s]ubstantial controversy, in the words of the NRC report). (NRC rep., supra, at p. 74.) Even Science, which purportedly sought balance in its coverage of this dispute by commissioning the Chakraborty-Kidd article as a rebuttal to the Lewontin-Hartl article (Roberts, Was Science Fair to its Authors? (Dec. 20, 1991) Science, at p. 1722, recognized that the competing articles seem likely to reinforce the notion that the [scientific] community is indeed divided under the Frye standard. ( Fight Erupts, supra, at p. 1723.) Our task under Kelly [15] - Frye is not to choose sides in this dispute over the reliability of the statistical calculation process. Once we discern a lack of general scientific acceptance  which in this instance is palpable  we have no choice but to exclude the bottom line expression of statistical significance in its current form. Barney, supra, 8 Cal.App. 4th at 814-19, 10 Cal.Rptr.2d at 740-43; accord, Pizarro, supra n. 12, 10 Cal.App. 4th at 78-90, 12 Cal.Rptr.2d at 451-58. The decisions in Barney and Pizarro are no aberrations. Although it is true, as the government contends, that the decisions admitting DNA match probabilities outnumber those reaching a contrary result, the imbalance is not as great (and certainly not as significant) as the government suggests. In a majority of the cases in which these match probabilities have been admitted, the defense failed to present evidence of the controversy among scientists which has since been recognized in the NRC REPORT and described in detail in Barney. [16] Indeed, the articles in Science magazine which focused attention on the controversy had not been written at the time that the cases on which the government relies were decided. [17] In Commonwealth v. Lanigan, 413 Mass. 154, 596 N.E.2d 311 (1992), the court, after discussing the NRC's recognition in its report of the current debate among population geneticists, concluded that the lively, and still very current, dispute described above regarding the role of population substructure constitutes something much more than a lack of unanimity. We cannot say that the processes by which Cellmark and the FBI estimated the frequency of the defendants' DNA profiles has found general acceptance in the field of population genetics. Accordingly evidence of the estimated frequencies of the defendants' DNA profiles is not admissible. Because the frequency estimates are inadmissible, evidence of a match between profiles is also inadmissible. Id. at 162-63, 596 N.E.2d at 316; (citation omitted). Similarly, in Bridgett, Judge Richter wrote that while the Defendant's contentions regarding the FBI's RFLP procedure are without merit, the issues raised concerning the FBI's calculation of probability estimates are meritorious. Several courts, including the Porter court, have excluded DNA evidence because of either the lack of consensus in the scientific community or the unreliability of probability estimates attached to the declaration of a match. Moreover, many scientific articles have been written on the issue both critical of and in favor of the calculation methodology employed by the FBI. 120 Daily Wash.L.Rptr. at 1704 (footnote [18] and citations [19] omitted). See also Vandebogart, supra, ___ N.H. at ___-___, 616 A.2d at 493-94; State v. Houser, 241 Neb. 525, 545-50, 490 N.W.2d 168, 182-84 (1992); Commonwealth v. Curnin, 409 Mass. 218, 220, 565 N.E.2d 440, 442-45 (1991); State v. Pennell, supra, note 5, 584 A.2d at 517-20. [20] To the extent that the decisions of the court and the magistrate in Yee, 134 F.R.D. at 165, 202, are to the contrary, we respectfully decline to follow them, especially in light of developments since Yee was decided. The government further argues that the FBI's probability calculation should have been admitted because the defense objections to it go to its weight and not to its admissibility. As the trial judge noted, however, the government ignores the fact that it is the probability feature which is at the very core of the DNA evidence. Porter, 120 Daily Wash.L.Rptr. at 506. Since a match between two DNA samples means little without data on probability, the calculation of statistical probability is an integral part of the process and the underlying method of arriving at that calculation must pass muster under Kelly/Frye. Axell, supra, 235 Cal.App.3d at 866-67, 1 Cal. Rptr.2d at 430. [W]e would not permit the admission of test results showing a DNA match (a positive result) without telling the jury anything about the likelihood of that match occurring. Curnin supra, 409 Mass. at 222 n. 7, 565 N.E.2d at 442-43 n. 7; see also Vandebogart, supra, ___ N.H. at ___, 616 A.2d at 494; Barney, supra, 8 Cal.App.4th at 816, 10 Cal.Rptr.2d at 742. Since the probability of a coincidental match is an essential part of the DNA evidence, and since there is no consensus as to the accuracy of the FBI's calculation, we decline to hold that the defense objections to that precise calculation go only to its weight. But see State v. Pierce, 64 Ohio St.3d 490, 494-97, 500-01, 597 N.E.2d 107, 111-12, 115 (1992) (distinguishing cases based on Frye and noting that Ohio does not follow Frye; court holds that objections to DNA evidence, which included prosecution experts' calculations of odds of forty billion to one against a coincidental match, go to the weight of such evidence but not to its admissibility). The lack of general acceptance among scientists of the proposition that the FBI's fixed bin methodology is sufficiently accurate to support a coincidental match probability of one in thirty (or forty) million, however, does not compel the conclusion that no probability estimate at all may be presented to the jury. As we explain below, demonstration of the existence of consensus among the appropriate scientists as to a more modest calculation would be sufficient.