Wilson

This murder case presents a narrow, but important, question regarding the admissibility of deoxyribonucleic acid (DNA) evidence to prove identity in criminal prosecutions. A DNA comparison of blood found at the crime scene with defendant’s blood resulted in a match. That is, defendant’s genetic profile matched that of the blood at the crime scene so that he could not be excluded as a donor of that blood. Similarly, a DNA comparison of blood found on the pants defendant was wearing when arrested resulted in a match with the victim’s blood so that the victim could not be excluded as a donor of that blood. Obviously, evidence tending to show that defendant’s blood was found at the crime scene, and that the victim’s blood was on defendant’s pants, would be highly probative to whether defendant was the killer.

When a match is found, the next question is the statistical significance of the match. Of course, a match is less significant if the blood could have come from many persons rather than from only a few. Experts calculate the odds or percentages—usually stated as one in some number—that a random person from the relevant population would have a similar match. The question…