A Riverside County jury is considering whether a convicted killer is mentally fit to stand trial for the murder of a 10-year old boy in 1997.

District attorney spokesman Michael Jeandron says opening statements began Monday in the mental competency trial of Joseph Edward Duncan III. Jeandron says the trial is expected to last four weeks.

A judge decided earlier this year to suspend criminal proceedings against Duncan until his mental competency is determined.

Duncan is accused of kidnapping Anthony Martinez as he played with his brother near their Beaumont home. The boy's nude and battered body was found about two weeks later in the desert east of Los Angeles.

Duncan was convicted of murdering a couple and two children in Idaho in 2005. He has received three death sentences.