Is it correct to state that, had the valve on the flight deck been set in the correct position for flight, then the tragedy would not have happened in the normal course of events (ie, in the absence of other unrelated causes)?
Is it correct to state that the routine pre-takeoff check list on that a/c includes ensuring that the valve is set in the correct position for flight?
Would it then be correct to conclude that the position in which the valve had been left by the maintenance engineer, who was convicted, would have been irrelevant if the flight crew had correctly and conscientiously carried out the necessary routine checks and acted on what they found -- ie, either set it appropriately for flight, or confirmed that it was already appropriately set?
Connetts is bang on with this statement. Almost every time I receive an aircraft from maintenance I find switches in the wrong position or just turned off, it is my responsibility to set the panel in the correct configuration, that is why I do a preflight.