The pilot is THE flight crew member........ full stop. He is ASSISTED by the observers who should assume the tactical navigation for the sortie and police job at hand.
While that is technically correct what about human factors angle?
The pilot might be responsibly but he is expecting the observer to be warning of hazards.
Is that a power line I see before me? I'm not sure....No it can't be
my observer is good and would have said something...