I was always taught that the prime purpose of the pilots' pre-flight check was to ensure that everything was configured correctly for a safe flight. Therefore, regardless of what had been done before, it is the pilot's responsibilty.
To hold the engineer responsible is totally against common sense, even if he had left the switch in the wrong position. I don't know anything about Greek justice but someone must intervene to prevent him being found guilty.
As others have said, the criminalisation of accident investigation flies in the face of fllght safety.