Prosecutors formally charged Holmes on Monday with 24 counts of first degree murder, 116 counts of attempted murder, and one charge of possessing an explosive device.

The 24-year-old faces two murder charges for each of the 12 people he is said to have killed – one for their deliberate killing and another for killing with "depraved indifference" to the lives of his victims.

Prosecutors said they would not decide for several weeks whether they would seek the death penalty, which can be used in the state of Colorado.

A further 58 people were injured in the shooting at a cinema in Aurora, near Denver on July 20. Ten of them are still in hospital, four in critical condition. The shooting took place at a midnight showing of the latest Batman movie.

District Chief Judge William Sylvester barred video and still cameras from Monday's hearing in the city of Centennial. He has since ordered that all details pertaining to the case be sealed and kept private - an apparent bid to ensure a fair trial amid the vast attention paid to the shooting. Several media outlets have challenged this court order for privacy.

msh/mz (AFP, AP, dpa, Reuters)