A number of you have pointed to this article, where Sheldon Whitehouse speaks of the corpus delicti that justifies an investigation.
The prosecutor is often first presented with a case as a "corpus delicti" — a bullet-riddled body in the street, for instance. That ordinarily is enough to justify investigation. Through investigation, the evidence may prove that there was not in fact a crime (it was a suicide or an accident) or that the fatal acts were privileged or enjoy a legal defense (self-defense or justifiable shooting by an officer of the law). But one begins by investigation.
Here he is on KO tying the dead bodies of torture right to Dick Cheney.
As he says,
If you don’t have anything to hide, you don’t often spend a great deal of time trying to hide it.