Colorado theater shooting defendant James Holmes is returning to court as his lawyers challenge possible trial testimony about computer analysis and data.
A judge is set to hear arguments about the issue Thursday and Friday.
Holmes is accused of killing 12 people and injuring 70 when he opened fire on a packed movie theater in the Denver suburb of Aurora in 2012.
His lawyers have acknowledged he was the shooter. Holmes pleaded not guilty by reason of insanity to more than 160 counts of murder and attempted murder.
Prosecutors are seeking the death penalty.
Police seized Holmes' computer equipment after the shooting. Holmes' lawyers are challenging testimony from experts who examined the equipment, saying prosecutors must show the testimony would be reliable.
Jury selection is scheduled to start in February.