In forensic cases, however, which consist of accusation and defence, there is one kind of conjecture by which we enquire both about an act and about its author. This sometimes treats the two questions together, as, for example, when both the act and the identity of the author are denied, and sometimes separately, as when the first enquiry, whether the act was committed, is followed by a second, where, the act being admitted, the question is by whom it was committed.