“And what we have now is evidence that chemical weapons have been used inside of Syria, but we don’t know how they were used, when they were used, who used them. We don’t have a chain of custody that establishes what happened.”
“Chain of custody” is a legal term: in a criminal trial the prosecution needs to show through sworn testimony that an item to be introduced into evidence is the same as the item taken at the scene of the crime or off the person of the defendant. We require such evidence because the government’s burden of proof is high: it must convinced a jury that the defendant is guilty beyond a reasonable doubt.
That’s not an appropriate standard for a nation-state considering whether to take action against another country. It’s a standard that in this case can surely never be met. Presidents have to act on incomplete and imperfect information in war and in considering whether to wage war. Obama is treating use of chemical weapons as a criminal offense and Syria as the scene of a possible crime.
And who is the jury Obama believes we must convince? After two more sentences, he said this: “And if we end up rushing to judgment without hard, effective evidence, then we can find ourselves in a position where we can’t mobilize the international community to support what we do.” This sounds like the “global test” John Kerry said the United States must pass in one of the 2004 presidential debates.