A null hypothesis is assumed to be true (he's alive) until there is overwhelming evidence for the alternative hypothesis (he's dead).
If our generals thought the way you do, they'd all be relieved of command.
Im fairly certain they DONT think like I do. Im sure they think in the context of UBLs successor(s). Sorry, Osama mystique doesnt work on me. Again, not one video of him after Dec 2001. Just scratchy audio tapes.