Kaylee Goncalves, Madison Mogen, Xana Kernodle and Ethan Chapin were found dead in a Moscow, Idaho, rental home in November.
Journalist Howard Blum joined “NewsNation Live” to explain the process behind how a Texas lab used specialized “proprietary devices” to examine the DNA on a knife sheath found at the house.
This lab, Blum said, has never before been used in an open case — just cold cases.
“This was the first time they were willing to take a chance,” he said.
Watch the full interview with Howard Blum in the video above.