There''s a theory that the first 48 hours after a homicide are the most crucial in solving a case. The longer a case goes unsolved the more difficult it becomes to unravel. Detailed here is the investigative work used to warm up cases that have gone cold. Students will learn how DNA evidence can be used to reopen an investigation and how experts can examine the details of previous investigations to find new leads. Sidebars offer descriptions of unusual cases and historical crime-solving breakthroughs.