A trial began Monday in Guam for a man charged with killing three Japanese and injuring 11 other people when he rammed a car into a crowd of tourists and then attacked bystanders with a knife.

The trial of Chad Ryan De Soto, 22, was opened by Judge Anita Sukola after 12 permanent jurists and six alternates were chosen. It is expected to run daily through July.

De Soto has pleaded not guilty on grounds of mental illness. His alleged victims were predominantly Japanese tourists, but the attack also left one female resident injured.

The attack took place in Guam's main tourist area of Tumon on Feb. 12, 2013. More than 100 witnesses are expected to be presented by the prosecution and the defense, with some of them traveling to Guam from Japan, Australia and the U.S.