Opinion ID: 2389693
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Heading: General Admissibility of Expert's Mathematical Calculation of Probability of Paternity

Text: Because the issue was neither tried nor raised before us, we do not decide whether the probability of paternity opinion, based on Bayes' Theorem, is sufficiently reliable to warrant its use in criminal cases to prove paternity. Its use in civil paternity proceedings appears to have legislative authorization. See N.J.S.A. 9:17-52c (permitting evidence of the statistical probability of the alleged father's paternity). Opinions based on Bayes' Theorem, however, are far from universally accepted for forensic purposes, especially in criminal cases. As noted below, we leave the determination of the admissibility of the probability of paternity opinion to the trial court after a full hearing of the matter. Without meaning to foreclose examination of any issue that the trial court deems relevant in making the admissibility determination, we suggest that the precise issue is rather narrow. We believe, from our readings, that Bayes' Theorem, when applied in conventional probability analysis, is practically universally accepted as valid  certainly sufficiently accepted to conform to any requirement of general acceptance in the relevant scientific community. See Probability and Inference in the Law of Evidence ix (Peter Tillers and Eric D. Green eds., 1988) ([E]ven the most rigorous critics of Bayesianism do not argue that Bayes' Theorem is invalid); Peterson, Paternity Tests, supra, 22 Santa Clara L.Rev. at 682 (there is no dispute over the mathematical correctness of Bayes' Theorem). What is not at all clear is its general acceptance for the purpose of converting what is essentially a non-mathematical conclusion of a prior probability of guilt into a higher probability through the use of the formula. The controversy, rather than the general acceptance, concerning the use of the probability of paternity opinion and Bayes' Theorem or formula  indeed the evidentiary use of Bayes' Theorem at all  is best reflected in the scholarly articles on this issue. See generally D.H. Kaye, Presumptions, Probability and Paternity, 30 Jurimetrics J. 323 (1990); C.C. Li & A. Chakravarti, An Expository Review of Two Methods of Calculating the Paternity Probability, 43 Am.J.Hum.Genetics 197 (1988); L. Jonathan Cohen, The Role of Evidential Weight in Criminal Proof, 66 B.U.L.Rev. 635 (1986); Lea Brilmayer, Second-Order Evidence and Bayesian Logic, 66 B.U.L.Rev. 673 (1986); Stephen Fienberg & Mark J. Schervish, The Relevance of Bayesian Inference for the Presentation of Evidence and for Legal Decisionmaking, 66 B.U.L.Rev. 771 (1986); Leonard J. Jaffee, Of Probativity and Probability: Statistics, Scientific Evidence, and the Calculus of Chance at Trial, 46 U.Pitt.L.Rev. 925 (1985); Craig R. Callen, Notes on a Grand Illusion: Some Limits on the Use of Bayesian Theory in Evidence Law, 57 Ind.L.Rev. 1 (1982); Michael O. Finkelstein & William B. Fairley, A Bayesian Approach to Identification Evidence, 83 Harv.L.Rev. 489 (1970). The intensity and complexity of the dispute is mind boggling on occasion for those other than mathematical experts. Indeed, even the experts have difficulty with it. One, for instance, referred to the Bayes' Theorem in 1987 as the reigning view, D.H. Kaye, Apples and Oranges: Confidence Coefficients and the Burden of Persuasion, 73 Cornell L.Rev. 54 (1987), but five years earlier had described it as not used as widely as the classical theories. D.H. Kaye, The Numbers Game: Statistical Inference in Discrimination Cases, 80 Mich.L.Rev. 833, 853 (1982). This same authority, Professor Kaye, although apparently supportive of the use of the formula to establish probability of paternity in 1979, Ellman & Kaye, Probabilities and Proof, supra, 54 N.Y.U.L.Rev. at 1149, expressly suggested its exclusion in criminal cases in 1987, D.H. Kaye, The Admissibility of Probability Evidence in Criminal Trials, 27 Jurimetrics J. 160, 172 (1987). The disagreement on the subject is such as to prevent us from reaching any conclusion about general acceptance. What is needed is what the trial court will have: examination and cross-examination on that issue. It boils down to this: you have a mathematical formula that invariably works in converting a mathematical statistical probability into a new probability by using in that formula new information about the matter, here the likelihood ratio based on the blood-tissue tests. The question is whether the formula produces reliable results when it is applied to a jury's conclusion about the prior probability  for instance when a jury, let us say in this case, concludes that even without the blood-tissue tests it believes defendant is guilty, that he is the father, and it quantifies that belief by saying that it is 60% probable that he is the father. Ordinarily, a 60% probability means that out of ten chances, the event in question will occur six times, but not the four other times. But what does a 60% probability mean in this case other than the strength of the jury's belief in guilt? That is just the beginning of the argument. One of the ends of the argument is the meaning of the ultimate figure  here that the probability of paternity is 96.55%. The expert translates that into very likely, based on the verbal predicate set forth in the Joint AMA-ABA Guidelines. Joint AMA-ABA Guidelines, supra, 10 Fam.L.Q. at 262. To a layman, 96.55% probability seems to correspond to something much stronger, highly likely, almost certain. But how is the jury to relate that percentage to the governing standard: beyond a reasonable doubt? The formula is helpful, if one considers it helpful, because it tells the jury in mathematical terms just how strongly the blood-tissue tests may be deemed to point in the direction of paternity  here, converting an assumed probability of 50% into one of 96.55%. If valid, the expert's opinion performs a service in helping the jury in such a case, for jurors presumably will have great difficulty in figuring out the significance of the likelihood ratio. Put differently, although the jury will intuitively and logically understand that the exclusion of 99 out of every 100 males as possible fathers increases the likelihood that defendant is the father, the jury will have difficulty in assessing just how much that likelihood is increased. The need for help in making that assessment is underscored when the typical arguments about the exclusionary percentage are considered  arguments so often made that one writer calls them the prosecutor's fallacy and the defense attorney's fallacy. William C. Thompson & Edward L. Schumann, Interpretation of Statistical Evidence in Criminal Trials, The Prosecutor's Fallacy and the Defense Attorney's Fallacy, 11 Law & Hum.Behav. 167, 170-72 (1987). The argument often made or implied by the prosecutor is that because there is only one chance in a hundred that the defendant would have this blood type if he were not the father, the jury may conclude that there must be a 99% chance that he is the father. The defense attorney's argument is that if one out of every 100 men has this blood-tissue type, then because the city where the crime occurred has one million people, there are presumably 10,000 people with that same type, 5,000 of them men  and the odds against defendant being the father are therefore 4,999 to 1. The defense argument, according to one study, is found more persuasive than the prosecutor's. Id. at 171. The conflict between the two arguments shows the jury's need for help in evaluating the significance of the exclusionary percentage. That need provides the justification and reason for the admission of the opinion and calculation of probability of paternity. For all of these reasons, the trial court should conduct an Evidence Rule 8 hearing, determining the expert's qualifications and the satisfaction of the conditions attached to the admission of expert testimony, i.e., general acceptability (see Rubanick v. Witco Chemical Corp. 125 N.J. 421, 454, 593 A. 2d 733 (1991)). The court may also decide that an Evidence Rule 4 hearing is needed. Its purpose would be to determine if the value of the probability of paternity opinion is substantially outweighed by the amount of time it will take to develop it, or the danger of prejudice or confusion. Ordinarily, the conclusion that allows expert testimony in the first place  here general acceptability  is for the court. Furthermore, once it is made, depending on the circumstances, it can become the law for all future cases. We not only do not submit the question of the reliability of the breathalyzer to the jury, it is no longer even submitted to the court in a Rule 8 hearing. We would assume, but we are not certain, that if the trial court's Rule 8 hearing is comprehensive, that its determination of admissibility, if upheld on appeal, would have a similar effect, permitting the use of Bayes' Theorem in a criminal case involving the question of paternity in future cases. It is impossible, however, for us to conclude just how much of the conflicting evidence about the validity of Bayes' in such application should be submitted to the jury. The answer to that question may bear directly on whether a Rule 4 determination is needed, for it seems to us that if the admission of this evidence because it has achieved general acceptance nevertheless requires, as a matter of fairness, a two-day trial before a jury to allow the testimony of those who do not accept it, the potential of confusion and the consumption of time may argue against its admission. We distinguish here between the time consumption and lengthy presentation of technical evidence before the court in the Rule 8 hearing (in most cases irrelevant to the Rule 4 question, which is directed at proceedings before the jury) and the same factors as applied to the jury trial itself. Since we have visited the subject fairly recently ( Windmere, Inc. v. International Insurance Co., 105 N.J. 373, 386, 522 A. 2d 405 (1987); Landrigan, supra, 127 N.J. at 414, 605 A. 2d 1079; Rubanick, supra, 125 N.J. at 433-34, 593 A. 2d 733), we need only summarize the rules governing the admission of expert testimony. In New Jersey, the general acceptance by the relevant scientific community test, established in Frye, substantially is still the law in New Jersey. See Frye v. United States, 293 F. 1013, 1014 (D.C. Cir.1923); State v. Kelly, 97 N.J. 178, 210, 478 A. 2d 364 (1984). But cf. 1 McCormick on Evidence § 203, at 871-72 (4th ed. 1992) (noting that Frye test has lost much of its force); Fed.R.Evid. 702 (permitting admission of expert opinion if it assists trier of fact); Fed.R.Evid. 704(a) (allowing expert testimony on ultimate issue). Despite invitations to do so, this Court has explicitly declined to part from the general acceptance requirement, Windmere, supra, 105 N.J. at 386, 522 A. 2d 405, and presumably given a criminal case, would be even more reluctant. See State v. Johnson, 42 N.J. 146, 171, 199 A. 2d 809 (1964) (requiring reliability of expert opinion evidence to be clearly established). An exception to the general acceptance standard is found in toxic tort cases on the issue of causation. Landrigan, supra, 127 N.J. at 414, 605 A. 2d 1079; Rubanick, supra, 125 N.J. at 433-34, 593 A. 2d 733. Recognizing the difficulties of proof of causation of cancer, and the apparent injustice of denying all recovery where the proof, although falling short of prior standards, is persuasive, we have allowed expert testimony, even though not generally accepted, where the facts and data relied on are of the kind that comparable experts would rely on, if the methodology or techniques used in converting those facts into an opinion are based on methodology that is similarly recognized by such experts as sound. The general acceptance that is thought to impart sufficient reliability to the expert's opinion as to warrant its admission is shown through the testimony of experts, through authoritative scientific or legal writings, or through persuasive judicial opinions. State v. Kelly, supra, 97 N.J. at 210, 478 A. 2d 364. Our readings, as suggested above, leave us with substantial doubt whether any one of the three methods of demonstrating general acceptance is present here. We know that general acceptance does not mean absolute or universal acceptance, State v. Tate, 102 N.J. 64, 83, 505 A. 2d 941 (1986); State v. Johnson, supra, 42 N.J. at 171, 199 A. 2d 809, and that total infallibility of the scientific technique is not required. Romano v. Kimmelman, 96 N.J. 66, 80, 474 A. 2d 1 (1984). But if the bottom line is general disagreement rather than general acceptance, we doubt if the standard is satisfied. Clearly, the probability of paternity as derived from indices based on HLA serologic tests and computed with Bayes' Theorem has achieved considerable recognition in the scientific community. The Joint AMA-ABA Guidelines specifically allow for use of even the fifty-fifty assumption as a useful working hypothesis, with the acknowledgement that this assumption will not correspond to the facts in most cases of disputed paternity. Joint AMA-ABA Guidelines, supra, 10 Fam.L.Q. at 262. As noted above, there is almost universal support for the non -forensic use of Bayes' Theorem. Ante at 505-506. HLA testing is accepted generally in the scientific community as a reliable procedure for proving or excluding paternity. Commonwealth v. Beausoleil, supra, 490 N.E. 2d at 799. We note also the explicit statutory provision permitting the use of blood and HLA tissue tests to establish the positive probability of parentage, N.J.S.A. 9:17-51e, i.e., paternity, in civil paternity cases. That provision also allows [e]xpert testimony pertaining to these tests, ibid., suggesting that the probability of paternity opinion used in this matter is statutorily permitted in civil cases, although the statute is not that explicit. [6] The further statutory language allowing [t]he court, upon application and for good cause shown, [to] limit the admissibility of blood tests or genetic tests, ibid., effectively safeguards against any potential in civil cases for prejudice arising from test results, presumably including the probability of paternity opinion. Various civil cases, however, seem to assume its admissibility. See, e.g., Essex County Welfare Division v. Harris, supra, 189 N.J. Super. at 482-83, 460 A. 2d 713; Jones v. Jones, supra, 242 N.J. Super. at 200, 576 A. 2d 316; Middlesex County Board of Social Services, supra, 237 N.J. Super. at 323-24, 567 A. 2d 1019. More than that, the above-cited statutory provision is the result of changes in the federal law designed to increase recovery from fathers failing to support children receiving Aid to Families with Dependent Children (AFDC) payments. The Family Support Act of 1988 (codified at 42 U.S.C.A. §§ 651 to 69 (1992 Supp.)), requires states to meet minimum paternity establishment performance standards, id. § 652(g)(1), and enhances this capacity by providing improved federal funding for laboratory testing conducted by the states. Id. § 655(a)(1). Under the federal law, states must require the child and all other parties, in a contested paternity case, to submit to genetic tests upon the request of any such party, [7] id. § 666(a)(5)(B), except in cases where the applicant or recipient of benefits has good cause for refusing to cooperate as determined by the State Agency ... 42 U.S.C.A. § 602(a)(26)(B). Assuming the validity of this statutory direction in civil cases, see Winberry v. Salisbury, 5 N.J. 240, 244-45, 74 A. 2d 406, cert. denied, 340 U.S. 877, 71 S.Ct. 123, 95 L.Ed. 638 (1950), apparently requiring admissibility of the probability of paternity, we would be reluctant to deny the admissibility of expert opinion of genetic testing results in criminal cases simply because the burden of proof is different. Regardless of whether the opinion is offered in a criminal or a civil context, its reliability and its tendency to prove a fact would seem to be the same. It is worth noting that a party in a paternity proceeding (like a defendant in a criminal trial) is entitled to be tried before a jury. N.J.S.A. 9:17-49; R. 5:14-1. Obviously, however, liberty is involved in one case and not in the other. Furthermore, the considerations that prompted the statutory amendment in civil paternity cases may have been deemed to justify either a risk of error or other consequences not acceptable in criminal cases. See Windmere, supra, 105 N.J. at 378, 522 A. 2d 405 ([i]n the criminal context, conditions of admissibility must be `clearly established') (quoting State v. Johnson, supra, 42 N.J. at 171, 199 A. 2d 809). The quantification of the probability of paternity in the form of a number, while problematic even in a civil case  where we sometimes speak of the burden as more probable than not, i.e., more than a 50% probability  causes almost undefinable difficulties in a criminal case, since no one has convincingly equated proof beyond a reasonable doubt with a probability number. L. Jonathan Cohen, The Probable and the Provable 49-57 (1977). We believe the provision in the statute concerning civil paternity cases, therefore, is persuasive but not at all dispositive of the admissibility of this evidence in criminal cases. Our rules concerning the admissibility of expert testimony must still be satisfied, as well as any special considerations that may pertain to proof in criminal cases. Romano v. Kimmelman, supra, 96 N.J. at 80, 474 A. 2d 1; State v. Cary, 49 N.J. 343, 352, 230 A. 2d 384 (1967). Assuming the trial court finds the expert's calculation of the probability of paternity admissible, we note some questionable restrictions on that admissibility suggested in case law. Several courts have instructed juries that they must disregard a probability of paternity figure unless they first find that the defendant had sex with the mother in the relevant time frame and under circumstances conducive to pregnancy. E.g., Everett v. Everett, supra, 150 Cal. App. 3d at 1064, 201 Cal. Rptr. at 361-63; Commonwealth v. Beausoleil, supra, 490 N.E. 2d at 797 n. 18; People v. Pasko, supra, 540 N.E. 2d at 466. We, however, explicitly reject any notion that intercourse must be proved before the probability of paternity percentage can be admitted, especially where intercourse, not paternity, is the ultimate issue. The calculation  Bayes' Theorem  if valid, does not depend on any particular degree of confidence in the fact of intercourse. Some cases have suggested that where the probability of exclusion is under 90%, or the resulting probability of paternity under 95%, the opinion should be excluded. E.g., Commonwealth v. Beausoleil, supra, 490 N.E. 2d at 795-96; Kofford v. Flora, supra, 744 P. 2d at 1353; see also Imms v. Clark, 654 S.W. 2d 281, 287 (Mo. App. 1983) (prohibiting admissibility of probability of exclusion where less than 90%). Based on our understanding of the issue, we would reject those limitations. [8] They have no basis in science or in mathematics. In this case, the expert testified that, based on her interpretation of the Joint AMA-ABA Guidelines, a probability of paternity below 90% would not be useful. In fact, the recommended verbal predicates suggest only estimates below 80% are not useful, while the utility of estimates in the 80% to 90% range is undecided. Joint AMA-ABA Guidelines, supra, 10 Fam. L.Q. at 262. Nevertheless, if an expert wants to claim that the scientific community has concluded that a probability of paternity that is less than 95% is unreliable or irrelevant, the trial court of course will evaluate that testimony in a Rule 8 hearing. Although we doubt that there will be any such testimony, or that if presented, that it will be persuasive, we note that those proposed conditions show the extent to which the use of the Bayes' formula is not credited in the courtroom environment. But cf. National Institute of Child Support Enforcement, U.S. Department of Health and Human Services, Essentials for Attorneys in Child Support 366, 376 (1986) (noting use of Bayes' Theorem in calculating probability of paternity is method most familiar to the American court system). As a practical matter, the complex issues raised by admitting evidence of HLA test results in paternity and criminal cases are likely to become less and less important, indeed totally irrelevant, once acceptable scientific standards permit a broader forensic use of DNA fingerprinting. It is generally accepted that DNA identifying techniques will exclude from consideration the DNA sequences of all but identical twins, making DNA testing the functional equivalent of a fingerprint. Brad R. Byers, Comment, DNA Fingerprinting and the Criminal Defendant: Guilty or Innocent? Only His Molecular Biologist Knows for Sure, 58 Ohio N.U.L.Rev. 57, 58 (1989); Eric S. Lander, DNA Fingerprinting on Trial, Nature 501 (June 1989). The complexity of the DNA testing procedures, and the apparently largely unregulated practices of those genetic laboratories equipped to conduct DNA testing in criminal cases, raise questions at this time concerning the potential reliability of such evidence in establishing paternity in criminal cases. Leigh C. Lawson, Comment, DNA Fingerprinting and Its Impact Upon Criminal Law, 41 Mercer L.Rev. 1453, 1456 (1990); Peter J. Neufeld & Neville Colman, When Science Takes the Witness Stand, Scientific American 46, 53 (May 1990). But see United States v. Jakobetz, 955 F. 2d 786, 799-800 (2d Cir.1992) (affirming admissibility of DNA profiling evidence in criminal cases); Ronald J. Richards, Comment, DNA Fingerprinting and Paternity Testing, 22 U.C.Davis L.Rev. 609, 635-37 (1989) (advocating use of DNA fingerprinting to establish paternity).