It's been a while since I've read the previous report, but this is the first that I've heard about the pilot not having a valid medical. If that's the case then how much actual oversight did the operator have of it's operations? If the operator had the pilot's medical expiry date in their crewing system, then the pilot should not have been asked to do the flight.
I know it was a multi crew aircraft and that the Captain is ultimately responsible, but I don't think that the first officers roles and actions were covered in enough detail for this accident.
As much as the Captain is responsible, it seems that there may have been many Swiss cheese holes aligning in this operation and this accident is the result.