Sending anything to WikiLeaks, which provides information to anyone, is a pretty clear cut case of: * That he knowingly gave intelligence (indirectly) to the enemy. * That he was aware that his action would cause the intel to be published. * That he was aware that the enemy would have access to it.
They don't have to show any of this. As part of his security clearance he will have signed multiple NDAs that spell out exactly what he can and can't do with the information. To get a conviction all they have to show is that he released information in violation of the NDAs, which souldn't be that hard. Some of the charges might require more, but he will be convicted of at least that without much doubt.