Given that his total time is apparently less than 700 hours it's fair to say he was very new to the A320. As I explained previously, there have been other crashes of the A320 that were directly attributed to false readings of flight parameter sensors. In one case it was a pitot tube that froze up, giving the flight computer inaccurate data regarding the aircraft's airspeed. In this case the nose was lowered automatically by the flight computer in an attempt to gain airspeed. This incident happened in heavy, convective weather at night. The pilot's became disoriented because they were getting conflicting information from their instruments and the flight computer. The aircraft ultimately flew itself right into the ocean killing all on board. On another A320 crash the angle of attack indicator had been damaged by ice and reported false "nose high" information to the flight computer. This also caused the flight computer to put the aircraft into a rather steep descent, even though the aircraft was actually at cruising altitude, flying straight and level. The crew became disoriented and it flew into the ground. Perhaps the most notable and spectacular crash of an A320 came at the Habsheim Airshow in 1988 while performing for the crowd of thousands. The pilots were unable to override the flight computer when pulling out of a descent as they neared the ground in a fly-by and the aircraft crashed in a forested area near the airport, earning the A320 the nickname "The worlds most expensive chain saw".
The fact that the pilot was locked out of the cockpit doesn't mean this was a deliberate act. It is very easy to become overwhelmed if you are new to a very complex system. There are quite literally dozens of examples where pilots have ignored all sorts of warning alarms and buzzers and did exactly the opposite of what the alarm was telling them to do. If this low time pilot became disoriented because he could not override the flight computer it is entirely possible that he never heard the pilot beating on the door.
1)Inexperienced co-pilot
2)Overwhelmed co-pilot
3)The world's most expensive chainsaw
4)Experienced pilot having inadvertently been locked out.
I'm in no position to comment on numbers 1 through 3 while you,a pilot,are.However,on #4...I did some googling a few hours ago and found a video made by Airbus regarding their system that insures cockpit security.Among the things learned from that video is that it's easy to gain access *with* the cockpit's consent,fairly easily accessed in cases of cockpit crew being incapacitated and essentially *impossible* to access if the cockpit crew actively denies access.So,during the 6 minute descent the stewardesses *and* the senior pilot would have known the different procedures yet *still*,it would appear,failed to gain access.
Can you think of any plausible explanation to explain this apart from "an overwhelmed,inexperienced,co-pilot"? The Airbus video I saw clearly showed that it just takes a quick flip of a switch in the cockpit to deny access to anyone trying to use the "incapacitated crew" option for access.