After Art is shot and lying on the floor, Joe removes the cushion from a nearby chair, and places it under Art's head for comfort. The camera goes back to the other people in the room. When the camera comes back to Art, the cushion is no longer under his head.
It's highly unlikely that the court would have only one officer guarding three prisoners who are accused of felonies and even less likely that he would turn his back on them while they were alone in a small conference room.