Opinion ID: 2389693
Heading Depth: 1
Heading Rank: 3

Heading: Admissibility of Probability of Exclusion and Paternity Index Based on Defendant's Blood-Tissue Type

Text: Given the controversies that exist concerning this matter  the admissibility not only of the probability of paternity opinion, but of the exclusionary percentage itself, as well as suggested conditions required in other cases that must be satisfied before such evidence is admitted, see, e.g., Commonwealth v. Beausoleil, supra, 490 N.E. 2d at 795-97; Kofford v. Flora, supra, 744 P. 2d at 1353  we believe further comment is needed. The comment is intended for consideration by courts (and attorneys) facing these issues but is not intended to be binding unless explicitly indicated. Our observations are based on cases, texts, and articles that in other contexts might be adequate to anticipate and dispose of related problems without a comprehensive record before us in a specific case  and the record here is far from comprehensive. Those sources, however, not only disclose raging controversy but demonstrate a subject matter that, at certain levels, is so complex that we are reluctant to categorically dispose of the issues in the absence of a comprehensive adversarial proceeding, and especially so in the context of a criminal case. We therefore leave the initial determination of all of these issues  including the admissibility of the probability of paternity and appropriate conditions on its admissibility  to trial courts when these issues are presented and fully tried. Our comments are intended solely as guides and considerations, none of these matters having been briefed or argued before this Court. We provide this guidance because the questions involved will inevitably arise in future cases of this kind, including some criminal cases other than rape prosecutions, e.g., when blood and tissue type of defendant corresponds to type found at scene of crime. We note that the Appellate Division, in ruling on the admissibility of the probability of paternity opinion, properly ruled only on the propriety of the expert's assumption of a 50% prior probability. 236 N.J. Super. at 27, 563 A. 2d 1145. It did not become involved, and did not have to, with the question of whether that defect in the expert's testimony, if corrected, would have rendered the probability of paternity opinion admissible, and, if so, under what conditions. Furthermore, its observations concerning the admissibility of other evidence  the exclusionary percentages and the related paternity index  were dictum, id. at 25, 563 A. 2d 1145, because both parties agreed they were admissible. This dictum, with which we agree, requires further explanation. We explicitly note here that in addition to the probability of exclusion, the related paternity index  if that has been calculated  is admissible at trial. It is, in effect, an exclusionary percentage that is based on additional blood tissue information resulting in a different likelihood ratio  usually higher than it would be without that information. Kaye, Probability of an Ultimate Issue, supra, 75 Iowa L.Rev. at 89-91. As we understand it, the exclusionary percentage, calculated by reference to a table of frequencies among the relevant population, is the result of the battery of tests that are usually made on a blood-tissue specimen. Each test is presumed to be independent of the other, the net result being not simply the exclusionary percentage that results from a particular test, but the exclusionary percentage that results from all of them, one being multiplied by the other. The paternity index adds another element: it factors into the exclusionary percentage (which discloses the percent of the population that has the required blood-tissue type) the relative likelihood of that type being transmitted to the child, some blood-tissue types included within the 1% being more likely to be transmitted than other included types. In other words, the less refined exclusionary percentage reflects the fact, for example, that only one out of a hundred men within the relevant population have the blood-tissue type that the father must have. In a population of one million there are presumably 5,000 such men, any one of whom could be the father. Refining the blood-tissue type genetic analysis further, we learn that there are sub-types and that while any one of the 5,000 could possibly be the father, those within that group who have a certain sub-type are more likely than others to be, this greater likelihood being statistically measurable in having the effect of increasing the exclusionary percentage and the likelihood ratio. (Some sub-types within the 5,000 are less likely to be the father, and result in a lower likelihood ratio.) The paternity index is essentially this new likelihood ratio. Kaye, Plemel As Primer, supra, 24 Willamette L.Rev. at 871-73. The question of the permissible use of this kind of evidence is similar to that posed in Landrigan v. Celotex, 127 N.J. 404, 414, 605 A. 2d 1079 (1991). There, as here, the evidence consisted of two distinct elements: first, the non-statistical evidence (the decedent's exposure to asbestos, and the absence of other potential causative factors) indicating that asbestos might have caused colon cancer  all of that evidence comparable to the non-scientific evidence in this case tending to prove that intercourse occurred; and second, background associative factors  that it is more likely (in Landrigan, 1.55 was the likelihood ratio) that one exposed to asbestos will get colon cancer than one who is not  this statistical element of the case comparable to the evidence in this case of the greater likelihood that a man with a blood-tissue type of the defendant is 100 times more likely to be the father than a man chosen at random. In Landrigan, we concluded, that the epidemiological evidence  the statistical likelihood that asbestos might have been the cause based solely on the greater occurrence of colon cancer in those who are exposed to asbestos  could be used along with other non-statistical direct evidence to support a conclusion of causation. In this case, instead of simply giving the jury both sets of facts  the underlying facts of the case and the related statistical evidence  and leaving to the jury the determination of the significance when both sets are put together, as we did in Landrigan, here a mathematical computation is added to the mix, one that purports precisely to calculate the probability of the ultimate issue. [5] The point here is that there is nothing fundamentally new in the use of blood-tissue tests to support the conclusion of paternity. What is new is the question of the admissibility of this mathematical formula to guide the jury in its use of the test information.