Book excerpt: Real crime scene investigation is vastly more complicated, arduous, bizarre, and fascinating than TV's streamlined versions. Most people who work actual investigations will tell you that the science never lies -- but people can. They may also contaminate evidence, or not know what to look for in crime scenes that typically are far more chaotic and confusing, whether inside or outside, than on TV. Forensic experts will tell you that the most important person entering a scene is the very first responding officer – the chain of evidence starts with this officer and holds or breaks according to what gets stepped on, or over, collected or contaminated, looked past, or looked over, from every person who enters or interprets the scene, all the way through the crime lab and trial. And forensic experts will tell you the success of a case can depend on any one expert's knowledge of quirky things, such as: "The Rule of the First Victim": (the first victim of a criminal usually lives near the criminal's home) Criminals' snacking habits at the scene"Nature's Evidence Technicians," the birds and rodents that hide bits of bone, jewelry, and fabric in their nestsThe botanical evidence found in criminals' pants cuffs Baseball caps as prime DNA repositoriesThe tales told by the application of physics to falling blood drops. Forensic experts talk about their expertise and their cases here. They also talk about themselves, their reactions to the horrors they witness, and their love of the work. For example, a DNA analyst talks about how she drives her family crazy by buccal-swabbing them all at Thanksgiving dinner. A latent print examiner talks about how he examines cubes of Jell-O at any buffet he goes to for tell-tale prints. A crime scene investigator gives his tips on clearing a scene of cops: he slaps "Bio-hazard" and "Cancer Causing Agent" stickers on his equipment. And an evidence technician talks about how hard it is to go to sleep after processing a scene, re-living what you've just witnessed, your mind going a hundred miles an hour. This is a world that TV crime shows can't touch. Here are eighty experts – including beat cops, evidence technicians, detectives, forensic anthropologists, blood spatter experts, DNA analysts, latent print examiners, firearms experts, trace analysts, crime lab directors, and prosecution and defense attorneys – speaking in their own words about what they've seen and what they've learned to journalist Connie Fletcher, who has gotten cops to talk freely in her bestsellers What Cops Know, Pure Cop, and Breaking and Entering. Every Contact Leaves A Trace presents the science, the human drama, and even the black comedy of crime scene investigation. Let the experts take you into their world. This is their book – their words, their knowledge, their stories. Through it all, one Sherlock Holmesian premise unites what they do and what it does to them: Every contact leaves a trace.