Attorneys representing the suspect in the Colorado movie theater massacre are expected to use an insanity defense.

Lawyers for James Holmes said in court Thursday that he is "mentally ill," and they need more time to determine his mental status.

The 24-year-old is facing 12 counts of murder and more than 100 additional charges for the Colorado shooting rampage that left 12 people dead and 58 wounded.

Defense attorney Daniel King made the revelation about Holmes' illness as he argued that the defense needs more information from prosecutors and investigators.

"We cannot begin to assess the nature and the depth of Mr. Holmes' mental illness until we receive full disclosure," he said at a hearing.

Meanwhile, victims and their families worry the focus of the trial will be on Holmes, rather than his actions.

Prosecutors have yet to decide whether to seek the death penalty.