Forensic Fallacies and a Famous Judge

Abstract

Judge Richard Posner, one of the great quantitative legal minds of our time, relied on flawed and illogical arguments in several recent forensic science appellate decisions. He equated non-equivalent probabilities and offered non sequiturs to support his belief that fingerprint errors are rare. I speculate that his errors spring from cognitive biases that are activated when people are asked to support or prove that which we “know” to be so.

Keywords: errors, fallacy, fingerprint, forensic, Posner, statistical evidence