A compelling examination of a frontier where science meets the law. Levy, a former New York City prosecutor, was one of the first lawyers to specialize in using DNA evidence in criminal trials. He deftly leads the reader through a series of case studies, including the original use of DNA in a British rape-murder investigation that showed a suspect to be innocent even though he had confessed, and later helped bring the actual criminal to justice; also examined is the Central Park jogger case, in which Levy and other prosecutors had to show why DNA evidence that the defendants had not raped the victim should be ignored. Anyone whose patience with the O.J. Simpson trial is not exhausted should check out the careful and illuminating analysis here. Despite his background as a district attorney, Levy is consistently evenhanded, stressing DNA's value not only as a tool for convicting the guilty but as a means of exonerating the innocent; one of the cases he examines at length involves a rape for which a man spent years in a Virginia prison, only to be released after DNA taken from the crime scene raised a reasonable doubt as to his guilt. Levy also ably tracks the scientific and legal controversies that have defined the role of this quickly developing field. The discussions of such scientific questions as the structure of DNA and its analysis are sometimes too brief; such a short book could easily have been expanded to provide clearer explanations of phenomena that are interesting in themselves, even without the added drama of crime and punishment. There also is disappointingly little here about Levy's own experiences as a prosecutor in cases that turned on DNA evidence. A highly readable mixture of true crime and popular science that is much stronger on the former than the latter.