State v. Spann
New Jersey Supreme Court
617 A.2d 247 (N.J. 1993)
Relevant factsFree
Joseph Spann (defendant) was charged with sexual assault after an expert testified, using Bayes' Theorem, that there was a 96.55 percent statistical probability Spann fathered the victim's child. The expert built that number using an assumed "prior probability" of 50 percent, described as neutral, but admitted on cross-examination that she knew none of the other facts of the case. Spann was convicted and appealed, arguing the expert testimony was improperly admitted.
IssueFree
Whether expert opinion testimony on the probability of paternity that relies on an assumed prior probability as one input may be admitted in a criminal case.