Two recent cases--the O.J. Simpson murder trial and the investigation of President Clinton's relations with Monica Lewinsky--had brought DNA testing to the front pages, and various law-enforcement officials, including Attorney General Janet Reno, had proposed making DNA testing as widespread as the taking of fingerprints. This fascinating session focuses on the legal and logistical implications, but Mr. Levy also offers a breathtaking explanation of exactly what we're talking about: "Here we have this cell, which is really too small for us to imagine, and there's the 3-billion-rung structure within each cell in our body, that's identical in every cell in our body and yet unlike that of any other individual on the face of the earth.... It is ... individuation on a level that has almost theological implications to it."