Cristhian Rivera, who is accused of killing Iowa college student Mollie Tibbetts, pleaded not guilty to murder charges at his arraignment Wednesday. Tibbetts disappeared in July, launching an investigation that captivated the nation for a month before authorities found her body. When investigators closed in on Rivera, he allegedly led them to the young woman’s body in a cornfield. A criminal complaint alleges that Rivera confessed to chasing Tibbetts and blacking out, only coming to when he was unloading her body from the trunk of his car. He was arrested and charged with first-degree murder on August 21. Rivera’s trial is set to begin April 16 of next year.