DEDHAM, Mass. (AP) _ A teen-ager accused of fatally bludgeoning a classmate with a baseball bat for a thrill smiled while denying any knowledge of the boy's fate two days after the slaying, a detective testified.

''He was very calm, almost bored, sort of like, 'Don't bother me.' He grinned, when I asked if he knew where Shaun was,'' Detective John Devine said during the second day of Rod Matthews' trial in Norfolk Superior Court.

Devine said Thursday he questioned Matthews twice about 14-year-old Shaun Ouillette's whereabouts.

Prosecutors say Matthews, a 15-year-old being tried as an adult in the 1986 slaying, showed the body in the snowy woods to friends, who stayed mum for weeks.

Defense attorney John Philip White has not denied that Matthews killed his classmate. But White said Matthews was a mentally ill child from a troubled home and whose use of the prescribed drug Ritalin, used to counter hyperactivity in children, contributed to his actions.

Devine testified he went to Matthews' home after a bus driver said he had seen Matthews and Ouillette together the previous afternoon.

When asked where Ouillette was, Matthews, then 14, said he had not seen him the previous day and suggested he might be in a neighboring town, the detective said.

During later questioning, Matthews said he played pool at home with Ouillette on Nov. 20, two days before Matthews' initial questioning, but still denied knowing anything about his whereabouts, Devine testified.

Forensic pathologist George Katsas, who performed an autopsy, testified the victim had three head injuries, the largest six inches long, which fractured the skull.

Chemist Robert Pino of the state police crime lab said blood and hair on the bat matched Ouillette's.

Other former friends told a shocked courtroom Wednesday of viewing Ouillette's body only hours after a pre-Thanksgiving pep rally, then bicycling with Matthews to a shopping mall pizza parlor for a snack.

''He said it could happen to us. He said, 'You never know,''' testified Robbie Peterson.

The former friends said Matthews named several potential victims before settling on Ouillette, an overweight high school freshman who had moved to the community south of Boston a year earlier.