Tyree Lincoln Smith, 36, was ordered committed yesterday.
Smith apologised for killing Angel Gonzalez, whose mutilated body was found in a vacant apartment in Connecticut in January 2012, a month after he was hacked to death.
"I'm really sorry for what I did, that I couldn't be myself," Smith said. "It really had nothing to do with the other person."
His cousin, Nicole Rabb, has testified that she saw Smith in December 2011 carrying a bloody ax and chopsticks and wearing pants that appeared to have blood on them. She said Smith told her he killed a man with the ax, ate his brain and eyeballs and drank sake in a local cemetery.
A prosecutor and social worker urged the three-judge panel to protect society from him.