A Utah grief author's murder trial. Eyewitness drama in Florida. Plus, Nancy Guthrie and Olivia Lone Bear.

The highly anticipated trial of Utah mom-of-three Kouri Richins is finally underway. Prosecutors say she poisoned her husband with fentanyl. In Miami, jurors watch video testimony of an eyewitness who may have seen the killer of football player Bryan Pata. In Dateline Round Up, Nick Reiner enters a plea and a former American Idol contestant is arrested for murder. Plus, in light of her mother Nancy's disappearance, Savannah Guthrie calls for greater attention to missing persons cases. We share the story of Olivia Lone Bear, a young mother whose death is still unsolved. Nancy Guthrie Tipline: 1-800-CALL-FBI (1-800-225-5324) Unresolved: The Case of Olivia Lone Bear: https://www.nbcnews.com/dateline/video/unresolved-the-case-of-olivia-lone-bear-119617605728 Find out more about the cases covered each week here: www.datelinetruecrimeweekly.com