I am agnostic about all the forensics—the Grassy Knoll, the Magic Bullet, the autopsy, all of it. But the one irreducible fact that any theory of the case must account for is Jack Ruby. Somebody, somewhere, needed Oswald silenced. The Warren Commission account, that Ruby did it out of compassion for the grieving widow, Jackie, to spare her from having to come back to Dallas and testify at Oswald’s trial, doesn’t hold water.