**This book explicitly chronicles 40 cases of unsolved murders and disappearances over a period of more than 160 years, tracing the evolution of criminal investigation and forensic techniques.** Murders and other violent crimes often leave an indelible mark on society. The 18th-century murder of Beautiful Cigar Girl Mary Rogers helped the then newly emerging tabloid papers become a fixture in the United States. The Federal Aviation Administration was spurred into requiring electronic screening of passengers and carry-on luggage by a series of highly-publicized hijackings. Abductions of youth gave birth to Amber Alerts and advertising missing children on milk cartons. And popular TV shows like *Law and Order* , *CSI* , and *Cold Case* document our fascination with police investigations, heinous criminals, and the complicated aftermath of their actions. This book examines 40 well-known cases of unsolved murders and suspected abductions over a period of over 160 years. Cases are organized chronologically to give readers insight into the evolution of criminal investigation techniques and forensics in the last century and a half. Later chapters detail how modern forensics were used in attempts to solve old cold cases or helped generate new leads.