Batman Shooting Suspect 'Mentally Ill'

Lawyers for the suspect in the deadly shootings at a Batman screening say he is mentally ill and have asked for more time for him to be assessed.

James Holmes has again appeared at a Colorado court with the same dazed demeanour he had at previous hearings.

The 24-year-old former PhD student at the University of Colorado is accused of the July 20 rampage at a midnight showing of the latest Batman film in Aurora.

Twelve people were killed and 58 injured.

Defence attorney Daniel King argued lawyers need more information from prosecutors and investigators to assess their client.

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

Mr King said Holmes had sought out a university psychiatrist, Lynne Fenton, for help but there were no further details.

Another hearing was scheduled for August 16 to establish whether there is a doctor-patient relationship between Dr Fenton and Holmes.

Legal analysts expect the case to be dominated by arguments over Holmes' sanity.

More than 20 media organisations have asked for a gag order barring the university from releasing details about Holmes to be scaled back, but prosecutors say releasing documents could harm their investigation.

Police have shared little of what they know about how Holmes prepared for the shooting, or how he rigged his nearby apartment with explosives.

Aurora police chief Daniel Oates has said the explosives were designed to kill anybody who entered, including emergency crews.