@hsxnl: Right on, why did the computer not issue a warning when a value goes from 1950 to -8 instantly. Surely the computer knows it is an airplane which can not do that in a few millisecs. The computer must also know that being on ground the value should be -2 so any value beyond -2 is BS. -8 is just plain a hardware fault.
Faulty system design leading to confusing the crew or in this case not notifying the crew clearly. You can debate if it was system and/or crew failure but if automation is to support and not cause death in this case I clearly go for system design fault.