In 2017, at 29 years old, Vallum was sentenced to 49 years in prison for Williamson's murder. Although Vallum had initially stated in court proceedings that he found out about Williamson being transgender shortly before he killed her in 2015, he later said in his plea hearing that he knew she was transgender for longer.

However, he kept that information, and the sexual nature of their relationship, a secret from friends and family.

According to Sun Herald, not long after Vallum admitted he killed Williamson, he was found in his jail cell after attempting suicide. According to the outlet, George County Jail employees found him unconscious with a bed sheet wrapped around his neck. There was also a note that said he had been "living a nightmare."

As of 2021, though, Vallum is still alive and in prison.

In 2018, Vallum appeared in the three-part BBC docuseries Love and Hate Crime, and although he said in the docuseries that he wished he could take back what he had done, he also claimed Williamson is now in hell.

"I know that I'm secure in my relationship with God but I don't know if Mercedes was secure," he said. "So I have to live with the fact that I killed Mercedes and she's in hell."