State v. Span

617 A.2d 247 (N.J. 1993)

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Nature of the Case

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Facts

D was a corrections officer at the Salem County Jail. The victim was incarcerated on a detainer from the Immigration and Naturalization Service. A 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. Under D's circumstances, intercourse itself is the crime, and here the proof of intercourse was strong. The only issue was whether D had intercourse with the prisoner. P presented evidence that D was the father of the victim's child. P used a human leukocyte antigen (HLA) tissue test to prove that D was the father. The expert knew absolutely nothing about the facts of the case other than those revealed by the blood and tissue tests of D, the victim, and the child. 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 D was the father. This placed the odds of D being the father -- wholly apart from the blood-tissue test -- at fifty-fifty. 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.' This opinion was based on a mathematical combination of three factors: the expert's assumed probability that D 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 Bayes' Theorem, the expert calculated the probability of paternity by multiplying the assumed odds. On cross-examination, D brought out the fact that the probability of paternity percentage was based on that fifty-fifty assumption. D noted that even if it were conclusively proven that D had been out of the country at the time when conception could have occurred, this expert still would have concluded that the probability D was the father was 96.55%. The expert's opinion had no relation whatsoever to the facts of the case. D was convicted and appealed. 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. The court reversed the conviction and P appealed.