Trials: The Laws of Probability

Around noon one day last June, an elderly woman was mugged in an alley in San Pedro, Calif. Shortly afterward, a witness saw a blonde girl, her pony tail flying, run out of the alley, get into a yellow car driven by a bearded Negro, and speed away. Police eventually arrested Janet and Malcolm Collins, a married couple who not only fitted the witness's physical description of the fugitive man and woman but also owned a yellow Lincoln. The evidence, though strong, was circumstantial. Was it enough to prove the Collinses guilty beyond...