majesty of the Princeps had become identified with that of the state, it might be employed as a convenient engine of judicial tyranny.[1842] Its utility was assisted by the unlimited and arbitrary character of its jurisdiction. It interpreted while it judged; it might extend the incidence of a law and frame new penalties; it might even punish in cases where no penalty was fixed by law;[1843] and the principle, forbidden in the _quaestiones_, of uniting several crimes in the same charge, was here admitted.[1844] This jurisdiction was technically, perhaps, a _cognitio_ of the consuls.[1845] But the Senate was their constant advising body, and the sentence took the form of a _senatus consultum_. We shall soon see how the Emperor’s presence at the board enabled him to influence a jurisdiction which was technically independent of his control. The voluntary jurisdiction of the Princeps in criminal matters was theoretically unlimited, and could be exercised at any time or in any place. It rested with him whether he would undertake the cognisance (_cognitionem suscipere_) at the request of one of the parties,[1846] or refer the case to the ordinary courts that is, to the _quaestio_ competent to try it. The relations of the two high courts of voluntary jurisdiction to the ordinary court of necessary jurisdiction, are admirably exemplified by the procedure adopted in the trial of Piso for the murder of Germanicus (A.D. 19-20). It is at the outset assumed that the case, which is one of poisoning, will come before the special commission established by the _lex Cornelia de veneficis_. But the Emperor’s cognisance is sought by the prosecutor, and Tiberius and his _consilium_ actually listen to the preliminaries of the trial. But the Emperor soon sees how invidious it will be to pronounce judgment in a case in which the murder of his own nephew and adopted son is the subject of investigation, and he, therefore, sends the matter unprejudiced to the Senate with a request that they should exercise their voluntary jurisdiction—a request which, coming from the Princeps, it was practically, although not legally, impossible for the Senate to decline.[1847] But, although any request for cognisance might be listened to, the Princeps usually confined his personal jurisdiction to certain spheres. These included serious crimes committed by members of the upper ranks in society, but especially offences committed by imperial servants or by the officers of the army.[1848] The Emperor might, of course, delegate this jurisdiction, although the delegation of special cases seems to have been unusual.[1849] On the other hand, the regular delegation of certain kinds of offences is frequent enough, and is the basis of the criminal jurisdiction of the Emperor’s servants, the various praefects who presided over the city, the praetorian guard, the corn-supply, and the watch.[1850]