New Jersey Supreme Court
617 A.2d 247 (N.J. 1993)
Joseph Spann (defendant) was charged with sexual assault. At trial, the prosecution presented evidence that Spann was the father of the victim’s child. Specifically, an expert testified that there was a 96.55 percent statistical probability that Spann was the father. The expert used Bayes’ Theorem, which was a valid theory of probability accepted in the mathematics community, to combine blood-test results and an assumed prior probability of 50 percent to arrive at a 96.55 percent probability of paternity. On cross-examination, the expert stated that the prior probability of 50 percent was used because it equally considered the positions of the victim and Spann on whether he was the father. The expert described this 50 percent factor as neutral and objective. The expert was unaware of any of the other facts in the case. Spann was convicted of sexual assault. Spann appealed, arguing that the introduction of the expert witness’s testimony was an abuse of discretion.
Rule of Law
Holding and Reasoning (Per curiam)
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