Karl Mayberry, 34, was arrested on May 7 and charged with murder for the 2021 death of his partner, 31-year-old Alvatyne Thomas. Investigators said they obtained phone records from Mayberry that showed he conducted online searches for 'first-degree murder defenses' and 'can 'he say, she say' be used against a person for murder in Missouri' at the time of Thomas' death.