Although Clarke spent much of his career as a prosecutor, he also covers cases where DNA evidence was used to exonerate. He directed a special project, proactively examining over six hundred cases of defendants convicted and sentenced to prison before 1993, with the goal of finding instances in which DNA typing might add new evidence and then offered testing to those inmates.

Databases of both convicted offenders and no-suspect cases demonstrate the power of DNA testing to solve the unsolvable. As Clarke tells the story of how he came to understand and use this new form of evidence, readers will develop a new appreciation for the role of science in the legal system.