On certification to the Superior Court, Appellate Division, whose opinion is reported at 236 N.J. Super. 13 (1989).
Chief Justice Wilentz and Justices Clifford, Handler, Pollock, O'Hern, Garibaldi, and Stein join in this opinion.
Defendant, Joseph M. Spann, was convicted of sexual assault, a second-degree crime under N.J.S.A. 2C:14-2c(3). The statute criminalizes sexual penetration when the defendant has supervisory or disciplinary power, by virtue of his "legal, professional or occupational status" and when the victim is "on probation or parole, or is detained in a hospital, prison or other institution . . . ." Defendant was a corrections officer at the Salem County Jail, where the victim was incarcerated on a detainer from the Immigration and Naturalization Service. Under those circumstances, intercourse itself is the crime, and here the proof of intercourse was strong, the verdict clearly sustainable even without the evidence challenged in this appeal. We find, however, as did the Appellate Division, that evidence was improperly admitted, and we cannot say that it was harmless. The admissibility of the evidence and harmless error were the only two points asserted in the State's petition for certification following the Appellate Division's reversal of the conviction. State v. Spann, 236 N.J. Super. 13 (1989).
As noted above, the only real issue, given the nature of the crime, was whether defendant had intercourse with the prisoner. Consent, force, or threats are irrelevant under the offense that was charged. The challenged evidence was that defendant was the father of the victim's child, conception clearly having occurred while she was imprisoned. If he was the father, criminal intercourse had occurred. The evidence consisted of blood and tissue tests, including human leukocyte antigen (HLA) tissue tests used to prove not that defendant was or was not excluded as the father but that he was the father. The specific item of that proof objected to by counsel was the State expert's opinion, based on those tests, that the "probability" of defendant's paternity was 96.55%. Obviously, that probability opinion, if improperly admitted, was highly prejudicial. If the expert's opinion were credited by the jury, unusually strong contradictory evidence would be required to overcome it. The expert's qualitative description of the percentage, expressed in non-mathematical terms (known as the "verbal predicate"), was that it was "very likely" defendant was the father. As stated by the prosecutor in summation, "guilt . . . is proved to a mathematical certainty . . . by carefully applying an objective scientific technique to the hard facts of this case."
The expert, testifying that the probability of defendant's paternity was 96.55%, knew absolutely nothing about the facts of the case other than those revealed by the blood and tissue tests of defendant, the victim, and the child, and that defendant was the accused.
Use of Blood-Tissue Specimens to Prove Paternity; Calculation of Probability of Paternity; Use of Calculation in this Case
Until relatively recently, blood-grouping tests to establish paternity were admissible only to exculpate the accused in paternity cases. N.J.S.A. 2A:83-3 (repealed by New Jersey Parentage Act, L. 1983, c. 17, § 23). Science had proven, and there is apparently no question about the validity of the proposition and certainly none raised in this case, that certain blood specimens completely exclude others. Thus, blood specimen "X," found at the scene of the crime and presumably that of the criminal, cannot come from an accused who has blood specimen "Y." Similarly, blood specimens from mother and child that conclusively determine that only a man with blood specimen "X" could be the father eliminate a man with blood specimen "Y." In such cases, if the accused's blood was excluded, he was innocent; in paternity disputes, he was not the father. In New Jersey paternity cases, this limited use of blood tests, to prove only that defendant was not the father, was codified in 1939. R.S. 2:99-3, N.J.S.A. 2A:83-3 (repealed). On the other hand, however, if the blood specimen was of the kind that could have come from the purported father, the evidence was apparently inadmissible to prove paternity.
The lack of probative force of this evidence for the purpose of proving paternity was thought to warrant its exclusion. Its identifying factor, the fact for instance that 50% of the population, including the accused, have blood that could have produced a specimen matching that of the father, was deemed too insignificant to justify admission if offered as independent proof of paternity, i.e., sufficient proof by itself. Even though insignificantly probative, it nevertheless was admissible as "a link in the chain of evidence" in criminal trials, just as the alleged assailant's blond hair is used against a blond defendant. See State v. Beard, 16 N.J. 50, 58-59 (1954) (holding type O -- the victim's blood type and also the most common type -- blood stains on defendant's clothing admissible as "link in the chain of evidence"); see also State v. Alexander, 7 N.J. 585, 593-94 (1951) (allowing evidence of defendant's blood type at murder trial for purpose of showing it was of the same type as blood found on the murder weapon), cert. denied, 343 U.S. 908, 72 S. Ct. 639, 96 L. Ed. 1326 (1952).
With the advent of multiple tests of blood samples, geneticists were sometimes able to exclude up to 72% of the population from certain blood types, i.e. given that kind of sample, those tests conclusively demonstrated that the sample could have come from only a limited portion of the population -- 28% of it. Joint AMA-ABA Guidelines: Present Status of Serologic Testing in Problems of Disputed Parentage, 10 Fam. L. Q. 247, 256-57 (1976) ["Joint AMA-ABA Guidelines"]. And with the discovery and development of HLA tissue testing -- a test not of blood alone but of tissues of all kinds -- the combination of blood and tissue testing, and on many occasions HLA testing alone, very often brought the exclusionary percentage to 95% and higher. Ibid.; D.H. Kaye, Plemel As a Primer on Proving Paternity, 24 Willamette L. Rev. 867, 868 (1988) ["Kaye, Plemel As Primer"]. In contrast to earlier blood-group testing, which had limited utility in identifying rare blood types, the advanced HLA systems enable geneticists to identify a rare blood type "in virtually every case."*fn1 Robert W. Peterson, A Few Things You Should Know About Paternity Tests (But Were Afraid to Ask), 22 Santa Clara L. Rev. 667, 675 (1982) ["Peterson, Paternity Tests"].
When the portion of the population excluded ran as high as, e.g., 98%, it became intuitively obvious that if only 2% of the population could produce that sample and defendant was part of the 2%, it was not only consistent with his guilt, but tended to prove it -- here that he was the father. Tests of blood and tissue samples started to be admitted not only to prove exclusion but also to prove paternity. See Essex County Welfare Div. v. Harris, 189 N.J. Super. 479, 482-83 (App. Div. 1983); J.H. v. M.H., 177 N.J. Super. 436, 441 (Ch. Div. 1980); Malvasi v. Malvasi, 167 N.J. Super. 513, 515 (Ch. Div. 1979). With an estimated one out of every six children born out of wedlock in this country, Kaye, Probability of an Ultimate Issue, supra n.1, 75 Iowa L. Rev. at 76 n.5, testimony revealing the probability of paternity becomes important, to society in general and to the welfare system in particular. Prodded by federal laws aimed at identifying fathers for child-support purposes where children received welfare benefits, New Jersey amended its parentage laws, for the first time allowing the court to require blood or genetic tests in contested paternity cases and to compel such tests when requested by a party. N.J.S.A. 9:17-51a. Whenever HLA tests are ordered by the court, they are admissible in evidence to establish "the positive probability of parentage." N.J.S.A. 9:17-51e. Moreover, "evidence relating to paternity may include . . . genetic or blood tests, weighted in accordance with evidence, if available, of the statistical probability of the alleged father's paternity". N.J.S.A. 9:17-52.
Precisely that kind of positive proof of paternity was used in this criminal case, as it had been in prior civil paternity cases without objection. See, e.g., Jones v. Jones, 242 N.J. Super. 195, 200 (App. Div.), certif. denied, 122 N.J. 418 (1990); Middlesex County Bd. of Social Servs. v. G.G., 237 N.J. Super. 322, 323-34 (App. Div. 1989). The State's expert stated that the blood and tissue samples, combined with statistical data reflecting the number of men with the relevant genes, excluded 99% of the North American black male population as possible fathers. In other words, only 1% of the presumed relevant population had the type of blood and tissue that the father must have had, and further, defendant was included within that 1%.
In calculating a final probability of paternity percentage, the expert relied in part on this 99% probability of exclusion. She also relied on an assumption of a 50% prior probability that defendant was the father. This assumption, not based on her knowledge of any evidence whatsoever in the case, placed the odds of defendant being the father -- wholly apart from the blood-tissue test -- at fifty-fifty. The fifty-fifty odds are usually expressed as "defendant being no more or less likely of being the father than any other man chosen at random." The claim of the victim (that defendant is the father) and the claim of the accused (that he is not) ostensibly are given equal weight. Or, as the expert stated in this case, "everything is equal . . . he may or may not be the father of the child." Based on the various tests, and the fifty-fifty assumption, the expert concluded that "the likelihood of this woman and this man producing this child with all of the genetic makeup versus this woman with a random male out of the black population . . . [results in] a probability of paternity [of] 96.55 percent."*fn2
This figure was conveyed to the jury to mean what it says -- this man is the father, or at least it is 96.55% probable that he is. It is not intended to and does not mean that he is part of a small group who might be the father (1% -- and if there are 100,000 men in the relevant population, that "small group" adds up to 1,000 men). It means that even though there may be 1,000 others who fit the bill, he is the father -- the odds are not 999 to 1 against the possibility of his being the father, but a 96.55% probability that he is.*fn3 If credited, the opinion is enormously persuasive.
The expert's opinion was based on a mathematical combination of three factors: the expert's assumed probability that defendant was as likely as any other man to be the father; the "probability" that a guilty suspect would have the required blood type (the probability here is 1, i.e., 100%, for whoever was "guilty," namely, the father, must have that blood type); and the probability that any man chosen at random would have that blood type (here 1%). Using a mathematical formula (Bayes' Theorem) apparently universally-accepted as valid in conventional probability analysis, the expert calculated the probability of paternity by multiplying the assumed odds (fifty-fifty, such odds being expressed as "1") by the relative likelihood of paternity as shown by the tests, called a "likelihood ratio" and calculated by dividing the probability of the incriminating results being found in a guilty suspect (1.0) divided by the probability that they will be found in an innocent suspect (.01). This multiplication (1 x 1/.01) gives the new odds: 100. Since odds of 100 means a probability of 100 out of 101 chances (odds of 3, for instance, means 3 to 1 or three out of four chances, a probability of .75), the probability thus calculated would be 99.01%. In fact, as noted above, the probability of paternity figure was 96.55%. Essentially, the formula the expert actually used included an exclusionary factor of 3.57% (not 1%) and would look something like the following:
The odds of 28 are the equivalent of a probability of 96.55%.
The reports of blood and tissue testing labs fairly regularly use this mathematical formula, calculating the probability of paternity figure based on the fifty-fifty assumption (that assumption sometimes referred to as the "prior probability," to convey the sense that it is the probability of defendant being the father based on all of the evidence in the case prior to any consideration of the blood and tissue test evidence). See Richard H. Walker, Guidelines for Reporting Estimates of Establishment, in United States Dep't of Health and Hum. Servs., Essentials for Attorneys in Child Support Enforcement, app. C, 391, 392 (1986). Many of the experts who testify concerning the lab results also use the fifty-fifty assumption, following Joint Guidelines formulated in 1976 by the American Medical Association (A.M.A.) and the Section on Family Law of the American Bar Association (A.B.A.). Joint AMA-ABA Guidelines, supra, 10 Fam. L. Q. at 262.
On cross-examination defense counsel brought out the fact that the probability of paternity percentage was based on that fifty-fifty assumption. The expert described it as a "neutral" assumption. Since it supposedly favored neither the accused nor the victim, the expert said it gave the contention of each side (mother and purported father) equal weight and eliminated any subjectivity from the opinion. Her characterization of the evidence was that its "purely objective" nature was "one of the beauties of the test"; that it "makes no assumption other than everything is equal"; and that "the jury simply has objective information." According to her testimony, there was no taking of sides, no judgment on the facts of the case. Defense counsel saw it differently. Counsel noted that even if it were conclusively proven that defendant had been out of the country at the time when conception could have occurred, this expert still would have concluded that the probability defendant was the father was 96.55%. Counsel's observation was correct; the expert's opinion had no relation whatsoever to the facts of the case.
The Appellate Division ruled that the probability of paternity percentage was inadmissible to prove intercourse because, in that court's view, the calculation itself assumed that intercourse had taken place. 236 N.J. Super. at 26 (citing State v. Hartman, 426 N.W.2d 320, 326 (Wis. 1988)). Quite simply, the Appellate Division ruled that the State cannot prove intercourse through a formula that assumes intercourse, or put differently, the trier of fact cannot convict a defendant of a crime through a formula that assumes the defendant committed the crime. Ibid. That Conclusion, supported by language in some cases, e.g., In re Paternity of M.J.B., 425 N.W.2d 404, 409 (Wis. 1988); County of Sonoma v. Grant W., 184 Cal. App.3d 868, 872, 229 Cal. Rptr. 297, 301 (Cal. App.), judgment vacated, 187 Cal. App.3d 1439, 232 Cal. Rptr. 471 (Cal. App. 1986); Everett v. Everett, 150 Cal. App.3d 1053, 1064, 201 Cal. Rptr. 351, 362-63 (Cal. App. 1984); People v. Pasko, 540 N.E.2d 462, 466 (Ill. App. 1989), as well as by statements in articles on the subject, e.g., Peterson, Paternity Tests, supra, 22 Santa Clara L. Rev. at 685, was almost compelled by the record in this case -- the expert practically conceding the point and both counsel agreeing that intercourse was assumed in the calculation.
The Conclusion, however, is incorrect. The .5 prior-probability assumption (odds of 1) says only that the chance that defendant is the father is fifty-fifty, that it is just as likely that he is not the father as that he is, or that it is just as likely that he is as that any man chosen at random is. Those odds, for instance, are wholly consistent with a fact pattern that one and only one man had access to and intercourse with the victim and that one of two, and only two, men, including defendant, could possibly have been that one man, neither one more likely than the other to be the father. The fifty-fifty odds calculated into the probability of paternity percentage do not at all assume that defendant had intercourse with the victim; indeed, defendant might have been the one with no access to the victim. See Kaye, Probability of an Ultimate Issue, supra, 75 Iowa L. Rev. at 105 n.153 (noting .5 prior probability "does not assume that intercourse definitely took place"); Mark Ellman & David Kaye, Probabilities and Proof: Can HLA and Blood Group Testing Prove Paternity?, 54 N.Y.U. L. Rev. 1131, 1150 (1979) ["Ellman & Kaye, Probabilities and Proof"] (stating fifty-fifty assumption "equivalent to supposing that the universe of ...