Should Khalid Shaikh Mohammed be executed?

Khalid Shaikh Mohammed, the self confessed mastermind of the 9/11 attacks will finally stand trial at Guantanamo Bay. Will executing him (the logical punishment) give him what he wants and make him a martyr? Would it be better to keep him alive in prison, with no trial, no oportunity for him to tell the world what he did and why and just make him irrelevant?