A propulsive true-crime thriller about the first use of DNA fingerprinting to nab -- and ultimately execute -- an American murderer. Trial attorney Mones (When a Child Kills, 1991) has a surefire story line here, with fascinations wholly apart from the obvious tie-in to the O.J. Simpson case. Detective Joe Horgas is a blunt, pugnacious, 16-year veteran of the Arlington County (Va.) Police Department, the kind of cop who challenges superiors and alienates colleagues in monomaniacal round-the-clock manhunts. In December 1987 he gets the assignment of his career: to catch the man who raped and slowly strangled to death a 30-ish, white female writer living alone in suburban Arlington. Horgas immediately spots parallels between this case and other recent rape-murders in Arlington and nearby Richmond, but when he presents his theory of a single murderer -- a black parolee named Timothy Spencer -- to his fellow officers, they shoot him down. The FBI said to look for a white suspect, they tell him. Besides, one of those rape-murders had already been solved: David Vasquez, a young janitor of borderline intelligence, had confessed to the crime and was serving 35 years for it. So Horgas contacts Lifecodes, a laboratory located in Valhalla, N.Y., one of the pioneers of DNA profiling. Over the next ten weeks, Lifecodes tests blood and semen stains found at rape-murder scenes dating back to 1983. Finally, after an excruciating wait, they present their conclusion: Horgas was right. Timothy Spencer was indeed the lone ""South Side Strangler,"" and David Vasquez, despite his ""confession,"" was innocent. Horgas, the abrasive renegade detective, seems almost a fictional creation, but Mones brings to his story gritty, specific descriptions of high-tech forensics that will fascinate true-crime buffs and mystery fans alike. Novelistic suspense, strong characterization, plus state-of-the-art crime-solving add up to a natural for summer reading lists.