The account which Tacitus gives us of this trial is obscure, involved, and fragmentary, for the story is broken off at its most important point by an unfortunate lacuna in the manuscript.  The other historians add but little light with their brief phrases and passing allusions.  We do not therefore entirely understand either the contents of the charges, the reason for the condemnation, the stand taken by the accused, or the conduct of Tiberius with regard to the accusation.  It seems hardly probable that Agrippina and Nero could have been truly guilty of a real conspiracy against Tiberius.  Isolated as they had been by Sejanus after the retirement of Tiberius to Capri, they would scarcely have been able to set a conspiracy on foot, even if they had so desired.  They were paying the penalty for the long war of calumnies and slanders which they had waged upon Tiberius, for the aversion and the scorn which they had always shown for him.  In this course of conduct many senators had encouraged them as long as Tiberius alone had not dared to have recourse to violent and cruel measures in order to make himself respected by his family.  But such acts of disrespect became serious crimes for the unfortunate woman and her hapless son, even in the eyes of the senators who had encouraged them to commit them, now that Sejanus had reinvigorated the imperial authority with his energy, and now that all felt that behind Tiberius and in his name and place there was acting a man of decision who knew how to punish his enemies and to reward his friends.

The trial and condemnation of Agrippina and Nero were certainly the machinations of Sejanus, who carried along with him not only the senate and the friends of the imperial family, but perhaps even Tiberius himself.  They prove how much Sejanus had been able to strengthen imperial authority, which had been hesitating and feeble in the last decade.  Sejanus had dared to do what Tiberius had never succeeded in doing; he had destroyed that center of opposition which gathered about Agrippina in the house of Germanicus.  It is therefore scarcely necessary to say that the ruin of Agrippina still further increased the power of Sejanus.  All bowed trembling before the man who had dared humiliate the very family of the Julio-Claudii.  Honors were showered upon his head; he was made senator and pontifex; he received the proconsular power; there was talk of a marriage between him and the widow of Nero; and it was finally proposed that he be named consul for five years.  Indeed, in 31, through the will of Tiberius, he actually became the colleague of the emperor himself in the consulate.  He needed only the tribunician power to make him the official collaborator of the emperor and his designated successor.  Every one at Rome, furthermore, considered him the future prince.

[Illustration:  Remains of the House of the Vestal Virgins.]