Truth
The more you repeat something, the more it becomes true. Syria killed Hariri. Syria killed Hariri. Syria killed Hariri.
The first White House response to the killing implicated Syria.
Then the American ambassador to Damascus was withdrawn, but not before she showed her displeasure with Syria.
If I say "you know John, he'd never kill anyone, never ever, he's not a murderer", John could sue me for libel. Why? Because I've just accused him of murder by implication.
I think the US knows what they're doing. And they're doing it very well.
At least someone's happy.