In June 1989, 14-year-old high school student, Stephanie Isaacson, walked to El Dorado High School in Las Vegas, Nevada. On her way to school, she took a shortcut through a vacant lot so she wouldn’t be late for her first class. After school let out, Stephanie’s father became worried when his daughter didn’t return home. He called the school and found out she never made it to class that morning.

Later that night, her body was found at a sandlot just off the path she usually took to school. She had been sexually assaulted and strangled to death. The investigation to track down her killer spanned decades. It wasn’t until three decades later that investigators finally got the break they needed. And it came from the equivalent of just 15 human cells.