A man who decapitated his stepmother in her Burnsville home in 2005 has been found not guilty of murder by reason of mental illness.

Stephen R. Miles, 27, must remain, however, at the Minnesota Security Hospital in St. Peter, where he was committed in 2006 after being determined mentally ill and dangerous.

The not-guilty ruling, issued late Thursday by Dakota County District Judge Kathryn Messerich, had been considered likely after experts for both the prosecution and defense agreed Miles did not know right from wrong when he killed Maris Jo Miles, 68.

"You can't minimize how gruesome this was," Marsh Halberg, Miles' attorney, said Friday. "But the question is now: What can you do with this man?"

According to the 23-page ruling, Miles had been diagnosed in 1998 with "extreme paranoia." By 2005, his mental condition had worsened to a point where he wore a metal pot on his head for fear that a listening device had been implanted in his tooth and could be used to drag him through the roof with an electromagnet.

When he killed his stepmother, he not only beheaded her after striking her in the head with a hatchet, Messerich wrote, but then also put the head in a dishwasher. He had thought the head could be reattached, authorities say, and expressed surprise later that his stepmother had died.

The question of when or whether Miles is released from the security hospital will be the subject of periodic court reviews, the county attorney's office said.

Halberg said that the man who once was "zombie-like" in his relations with him now can make eye contact and has inflections in his voice.

"But it's not like they're going to open the doors of St. Peter and say, 'You're free,' " Halberg said. "He's going to need extensive rehabilitation."

Anthony Lonetree • 612-673-4109