Moving IR Spectroscopy Down to the Micron Level Puts Serial Killer Behind Bars

Infrared microscopy played a key role in putting the United States most prolific serial killer ever behind bars.

The killer had originally been arrested based on a DNA match but the circumstances raised questions as to whether that evidence would be enough to convict. Infrared microscopy provided a crucial additional link between the killer and his victims. The new evidence quickly led to a confession to a horrific series of crimes. On August 15, 1982 Robert Ainsworth stepped into his rubber raft and began to float down the Green River in the outskirts of Seattle. A few minutes later he peered into the clear waters and stared right into the eyes of woman floating on her back just beneath the surface of the water. Seconds later he saw another barely submerged corpse of a young woman. The police officers he called to the scene later found a third body in the woods near the river. In the space of six months, three other bodies of young women were found in and around the river. Police quickly realized that a serial killer was on the loose. Over the next several years, while investigators focused on an area in Seattle where many of the victims worked as prostitutes, many more women either disappeared or were discovered dead.

Then on April 30, 1983, came a break that would, 20 years later, lead to closing the case. A prostitute's boyfriend saw her get into a truck with a customer just before it sped away. Suspicious of the customer, he gave chase but lost the truck. It was the last time he ever saw his girlfriend. Less than a week later, he spotted the suspicious truck in the same area where it had picked up his girlfriend. He followed the driver home and called the police. Police arrived at the house and spoke to the owner, Gary Ridgway, who denied having seen the prostitute. Ridgway turned out to be a happily-married family man, so he didn't fit the psychological profile developed of the killer, and he passed a polygraph test, so police crossed him off the suspect list.