" Then we could collate all the possibles and go to work with the holy trinity of detectives everywhere: means, motive, opportunity. Means and opportunity wouldn’t signify much. By definition nobody would be on the possibles list unless they had been proved to have opportunity. And everybody in the army was physically capable of swinging a tire iron or a crowbar against the back of an unsuspecting victim’s head. It was probably a rough equivalent of the most basic entry requirement. "
― Lee Child , The Enemy (Jack Reacher, #8)