"Twenty years, nobody asked me," the operator tearfully explains in the clip, which debuted Tuesday. "I think it would have really turned the case around."
The trailer shows the investigators analyzing the phone call and reducing noise to hear a conversation the happened when the mother thought the call had disconnected.
Parents John and Patsy remained suspects in their daughter's death until 2008, when police finally cleared their names. Sadly, Patsy had already been dead for two years after her battle with cancer.
JonBenet’s older brother Ramsey is also set to appear in an upcoming special with Dr. Phil, speaking publicly for the first time.
The three-part series will air in September.
This article first appeared on Marie Claire.