A teenage boy who had been working inside a garage heard his dog barking and the sounds of a car door slamming outside. The boy left the garage and noticed an orange Datsun station wagon parked across the road, an unfamiliar vehicle in the Orange County suburb of Mission Viejo. Suspicious, the boy made a mental note of the station wagon's license plate. When police arrived at the house where the Datsun had been spotted earlier that night, they discovered two victims. The perpetrator shot 29-year-old Bill Carns five times in the head, and raped his fiancEe. The next day police found the orange station wagon and, thanks to a recently acquired argon-ion laser, authorities would link a palm print inside the car to Richard Ramirez, a 25-year-old drifter from Texas who had a penchant for Satanism and drug abuse. Every day, forensic scientists around the world have the unenviable task of investigating crime scenes such as the one by the reputed Night Stalker described above. They examine homicides, hit-and-run accidents and sexual assaults. Invariably, the perpetrators of these crimes leave their mark, often in the form of fibers, bodily fluids, gunshot residues and traces of illicit drugs. It is the task of police to gather evidence and investigate the seemingly invisible trail left behind. In the past, police relied on course black powders used to dust for prints and high-intensity lights to inspect the scene. As technology has advanced, investigators are beginning to rely on alternate light sources and high-power lasers that pick up the faintest fingerprints and tiniest fibers. Increasingly, photonics has enabled police to crack even the most elusive cases.