A Reston man who beat his mother to death with a baseball bat last year--later telling doctors a chess piece had ordered him to kill her--was formally committed to a mental hospital yesterday. Alfred L. Head, 22, will be reevaluated regularly by a Fairfax County judge to determine whether he is fit to return to society.

Head never publicly explained what drove him to crash his 1990 Pontiac into the living room of his family's home in July 1998 and attack his mother, Zona N. Head, 56. But at his trial in October, mental health experts testified that he was suffering from schizophrenia and bipolar disorder and that he was acting on the orders of a chess piece. He was found not guilty by reason of insanity.

Head did not speak yesterday at his hearing before Circuit Judge Stanley P. Klein.

Commonwealth's Attorney Robert F. Horan Jr. did not contest Head's insanity plea or Klein's decision to commit him to Central State Hospital in Petersburg for a year. Head "is mentally ill at this time," Klein said. "There is a likelihood that if he were released, even conditionally, he would engage in conduct that would result in bodily harm to himself and others."

For the next five years, doctors will submit annual reports on Head's mental health to the judge, who will then hold a hearing on whether Head should be released. After five years, hearings will be every two years.

Head's father, Alfred, was not in court yesterday. His attorney, Joanmarie I. Davoli, said the case "underscores the flaw" in civil commitment laws because, she said, Head's mother had tried to obtain help for her son but couldn't until he demonstrated that he was a danger to himself or others.

By the time he did that, Zona Head was dead.