James Holmes, accused in the Aurora cinema shooting last month has a 'mental illness', his defence attorney said in the court Thursday.

Holmes was present in a hearing in which a judge weighed a request by 20 media organizations to unseal documents related to his case.

During the hearing lawyer Daniel King repeatedly made references to his client's unspecified mental illness, giving the first clear sign that Holmes' lawyers might be considering an insanity defense.

Holmes is accused of bursting into a midnight screening of 'The Dark Knight Rises' in the Denver suburb of Aurora and opening fire in the crowded theater, killing 12 people and wounding 58 others.

"He tried to get help with his mental illness," King said of his client. The 24-year-old former neuroscience graduate student at the University of Colorado faces 24 counts of first-degree murder and 116 counts of attempted murder.

Holmes seemed alert but disinterested in his third appearance in a Colorado courtroom since the July 20 mass shooting. He mostly stared straight ahead and did not talk to his lawyers.

During the hearing Judge William Sylvester said he would consider a request by 20 media organizations to unseal and make public documents detailing the murder case against Holmes, and would issue a written ruling later.

But both the prosecutors and defense lawyers objected saying that it was too early to open the file because the investigation was still ongoing.

Court papers filed by defense attorneys two weeks ago said Holmes had been a patient of the medical director for student mental health services on campus, Dr.Lynne Fenton, before he filed paperwork to drop out of the competitive graduate program.

According to media reports, Fenton had contacted the university's threat assessment team and university police expressing concerns over the behavior of his patient weeks before the shooting. Last week, the University of Colorado announced it had appointed a former prosecutor to probe its dealings with the handling of the accused.

Holmes is being held without bond and in solitary confinement at the Arapahoe County jail.