The trial for a Mexican national charged with first-degree murder in the abduction and killing of Mollie Tibbetts has again been delayed.  25-year-old Cristhian Bahena Rivera will now face trial beginning February  4 in Sioux City. His trial had been set for November 12, but was pushed back to give expert witnesses more time to review new evidence.  Rivera is accused of killing Tibbetts, who disappeared while out for a run in July 2018 in her home town of Brooklyn. Investigators recovered her body a month later in a cornfield. Officials say she was stabbed to death.  Rivera is also accused of being in the country illegally. He worked at a dairy farm a few miles from where Tibbetts disappeared.