PEORIA, Ill. -- Defense testimony continued Tuesday in the mass murder trial of Christopher Harris.
Psychologist Dr. Craig Anderson says one of the victims, Dillen Constant, exhibited behavior linked to violence and aggression.
In reading from several reports, Anderson said Dillen, 14, had a history of physical and verbal aggression, suffered from attention deficit disorder and had low interest in school.
He said on two occasions Dillen pulled a knife on his sister, Justina, punched holes in walls and threw objects during angry outbursts.
The defense argues that Christopher Harris walked into the Gee family home on September 21, 2009, as Dillen was beating family members, and killed the teenager in self defense.
Dr. Anderson also testified that Dillen's violent behavior may be influenced by his use of violent video games, two of which Dillen played the night of the murders.
The defense is expected to call four witnesses on Tuesday. Christopher Harris' ex-wife, Nicole Gee, is expected to testify on Wednesday.
Defense attorney's say they will likely rest on Wednesday.