Despite derision in the press, DCS Twigg didn't let it get to him. He had to get Rufus to confess. It would make it all so much easier and Twigg correctly guessed that there were more murders they didn't yet know about executed by Rufus.
Rufus had been left in his cell to stew for a few hours before questioning. That was Twigg's modus operandi after he'd arrested and charged someone. He'd made sure Rufus stayed awake to lower his mental resistance - important because he was a very bright boy!
In his cell, Rufus, now holding his head, started screaming.