
The US Government is going to be using its own evidence
Obviously the USA's defence intelligence community tries to monitor internet traffic coming out of China. We know the USA monitors all internet traffic entering the USA.
With all that monitoring, and all that analysis, I think it is likely that the US government is determining its foreign policy primarily based on what it "thinks it knows" from what it has detected itself, as opposed to the theories of outsiders.
Of course the USA could be making a mistake. Personally, based on how China is known to treat people with differing opinions (what it calls dissidents and traitors), I think the Americans probably have this one right or partly right.
After all, make enough accusations and some are bound to be correct. It is just too bad Blair and Bush have destroyed the credibility of their respective homelands.
By the way, the article is incorrect on the level of proof required by US courts. In some civil cases a "balance of probabilities" is required, in other civil cases a "preponderance of evidence" is required. Only in criminal cases does a conviction requires "proof beyond reasonable doubt". Under international law, the level of evidence also varies depending on the kind of case.
And that one piece of evidence fails means nothing. The question is whether there is any good evidence.
Of course in this case the evidence will probably never be made public, because IF it exists it would embarrass China too much, and diplomats will see no point to doing that. Also because revealing the evidence would likely give insight into hour much privacy we all lost forever -- to what extent internet traffic is monitored by our governments -- because of decisions made and precedents set by US Republican President Bush and UK Labour PM Blair.