Marks and his girlfriend, Maya Maxwell, were indicted on capital murder charges as well as tampering with evidence in April in connection with the deaths of Jenna Scott and Michael Swearingin. Scott had been in a relationship with Marks but reportedly left him because he was abusive, according to family members.
The two victims were killed on Jan. 3 and their bodies were found on Jan. 15 in rural Oklahoma.
Marks was arrested in February but escaped a prisoner transport van before being recaptured later in the day.
Marks pleaded not guilty, and the Bell County District Attorney’s Office filed formal notice to seek the death penalty Monday.
Marks spent about 20 years as a professional MMA fighter, competing for XFC and Bellator among other organizations. He posted a 30-27 career record, with his last fight coming in March of 2018.