Unmasked: My Life Solving America's Cold Cases

Much of Unmasked centers on crime solving using forensic evidence retrieved from victims and crime scenes. Rudimentary forms of the kind of analysis forensic science provides date back to early human civilization, with the invention of pathology—performing autopsies to discover a person’s cause of death. The invention of the polygraph (known as the “lie detector test”) was a more recent development in the field, though today the test is considered flawed. This test measures physical responses such as increased heart rate and the presence of sweat when one is answering questions. Though such test results are not admissible in court cases today, they are still sometimes used to narrow a field of suspects. Another early form of forensic science came with the invention of fingerprint analysis in 1880. Each human being—even identical twins—has a unique pattern of lines and ridges on each fingertip, so studying prints left at crime scenes proved a way to determine suspects. Fingerprints are captured at crime scenes using different methods depending on the surface the prints appear on. In some cases, investigators photograph them with extremely high-resolution cameras. Often, surfaces are “dusted” for fingerprints, which involves spreading a dark powder onto a surface to make the prints appear.