Las Vegas investigators have identified a suspect in the 1989 killing of a 14-year-old girl by using the smallest set of DNA samples ever used to crack a cold case, the Las Vegas Review-Journal reports. Stephanie Isaacson went missing from Las Vegas after leaving her home to walk to school. Her body was found the evening of her disappearance; she had been sexually assaulted and strangled. Justin Woo, a local philanthropist, provided a donation that utilized new genome sequencing technology to analyze just 15 DNA cells that led to identifying Darren Roy Marchand as the suspected killer. Marchand had strangled a woman three years prior to Isaacson’s death. He died by suicide in 1995.

Despite the case taking decades to be solved, Isaacson’s mother said she was relieved. “I never believed the case would be solved,” she said in a statement.