Cheney on Stand?

According to this CNN report the defense for Pfc. Lynndie England would like to put Vice President Cheney on the stand. I believe that request must be honored, as well as those for any other witness, no matter how high a position they happen to occupy. The only reason not to honor it should be the absolute physical impossibility due to an extremely busy schedule. I think campaign speeches and other non-essential activities must be cancelled, if need be, lest that be necessary for the official in question to be able to testify.