Actually, the Scottish verdict would be handy in American criminal trials generally. Every defendant who beats the rap and gets a "not guilty" verdict immediately goes on TV to claim that he has "been exonerated." That garbage would be cut off at the knees if the jury had the authority to rule "not proven."
In that instance, there would be a clear distinction between "not guilty," which means "We the jury are satisfied that the defendant didn't do the crime" -- and "not proven," which means "We the jury believe the defendant did the crime, but there's not quite enough evidence to find him guilty."
However, that discussion of criminal law detracts not one bit from the general conclusion that Spectre is a doofus who doesn't belong in the Senate. I hope the premise of this article proves out.
Congressman Billybob