Something just doesn't add up with this accident. If I were the co-pilot and I wanted to deliberately crash the aircraft what I would not do is to use the autopilot and put the jet on a steady, controlled decent into terrain that took 8 minutes while the Captain is trying to break through the door. In my mind there would always be a chance he would get through the door and interfere with my plan. Why risk that? I would lock the Captain out of the cockpit, roll the aircraft inverted, and dive the jet nose-first into the ground. Would take about 2 1/2 minutes from 38,000 feet but more importantly the increase in speed would begin to rip parts off of the aircraft long before I neared the ground ensuring I succeeded in my goal.
If we consider that this co-pilot was committed enough to die to watch the ground coming at him through the windscreen for 8 minutes and do nothing then we can assume he was very committed to dying. Why would he risk failure? Yes, I understand the doors are "impenetrable," but still it is a sloppy plan. It just doesn't fit for me.