By 'evidence' I mean all evidence relevant to the case. Obama's citizenship isn't part of that since he's not charges with disobeying Obama's order but that of his brigade commander.
Why did Congress pass court martial authority to the executive? Was it to help the President control the military by following orders. I submit all orders originate from the President via his authorized representatives...from the corporal, sergeant, staff sergeant, senior NCO’s and officers in the chain of command.
If there is no court martial a staff sergeant really does not have much power, that power comes from the President given to him by the Congress.