Centennial - James Holmes used a cellphone to take self-portraits the night that police say he shot up a Colorado cinema last year.
He stuck out his tongue, smiled and posed with a Glock pistol.
Police showed the photos in court on Wednesday, along with pictures of the cinema they say Holmes took a month before the attack.
One photo shows an exit door like the one investigators say Holmes propped open the night of the attack, which left 12 dead and at least 58 injured.
The testimony came as a hearing to determine if Holmes will stand trial neared an end.
Defence attorneys announced they would not call any witnesses.
They had been granted permission to call two witnesses to talk about Holmes' mental state.