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. They can be “lifted” from the surface with tape and then preserved. The collected prints are then compared to those on record in the FBI’s database, which was established in 1970s. The same principles can recover other kinds of pattern evidence, such as shoe prints or tire treads.

Modern forensic science, however, primarily focuses on assessing bodily fluids or materials, such as blood, skin, hair, semen, or saliva. One significant development in the field was the ability to assess blood type—another means of narrowing a field of suspects. All humans have one of four blood types, an aspect of human physiology that was studied as early as 1901 but not completely understood until the 1960s. It was the advent of DNA testing, however, that made forensic science a game-changing aspect of crime scene investigation. DNA, short for deoxyribonucleic acid, is the genetic code found within cells that makes each human the unique person that they are. Each person’s DNA is unique and can be extracted from cells found in blood, semen, hair, salvia, skin, or other bodily material. These types of bodily materials are often left behind at violent crime scenes. Beginning in the 1980s, DNA became a useful form of crime scene evidence, though it was not readily utilized until the late 1990s. As science advances, DNA extraction has become easier, even given microscopic amounts of bodily material. Unmasked demonstrates how such material, stored as evidence, can be used to solve previously unsolved cold cases, arguing for The Importance of Science in Crime Solving.