As the case became exclusively political, Plancina naturally dropped out of it; “machinations of Livia,” shrieked Agrippina, and Tacitus has repeated the shriek.
The case had an abrupt and tragic termination. Piso, seeing that the hostile evidence steadily accumulated, and that Tiberius preserved an absolutely impartial and judicial attitude, killed himself, leaving a letter to Tiberius, from which the following extract has been preserved: “Crushed by a conspiracy of my private enemies, and the hatefulness of a false accusation, inasmuch as no opportunity is left for the truth and the establishment of my innocence, I call heaven to witness, Cæsar, that I have lived loyally to you, and dutifully to your mother; and I implore you to take charge of my children, of whom Gnæus Piso was certainly not concerned in my fortunes whatever may have been their character, for he spent the whole time at Rome, and Marcus Piso dissuaded me from returning to Syria. And I wish that I had rather given way to the counsels of my young son than he to those of his aged father. I beg the more earnestly that his innocence may not pay the penalty of my perversity. I beg for the safety of my unhappy son in the name of forty-five years of loyal duty, of a consulship shared with yourself, of the confidence placed in me by Augustus, of the friendship with yourself, and as a last request.” He made no mention of his wife in this dying petition. Tiberius exempted Marcus Piso from any complicity in the charges brought against his father, and also spoke on behalf of Plancina. A two days’ inquiry was held into her conduct, but to the disgust of Agrippina she was acquitted. Her escape was attributed to the influence of Livia.
The Senate passed severe sentences upon the sons of Piso, which Tiberius, as usual, considerably modified. Honours and rewards were bestowed on the accusers, but Tiberius, in promising Fulcinius Trio office later on, significantly hinted that he was in danger of spoiling his eloquence by excessive violence. It had been in the power of Tiberius to confiscate the property of Piso, but he bestowed it upon his son Marcus. Tacitus comments in characteristic fashion—“Superior to the temptation of money, as I have often recorded, and the more readily appeased at that time through an uneasy conscience about the acquittal of Plancina.”
There certainly does not seem to have been any miscarriage of justice, for even if Piso was sincere in his protestations of innocence, and really was innocent of the technical offence of waging civil war, his case was never concluded, and he was never condemned. It pleased Agrippina and her friends, and it pleased the sensation mongers of the capital, to see in the case not a political trial, but a demand for vengeance on the murderers of Germanicus. In this demand they were disappointed, for Plancina, the supposed culprit, escaped altogether, Piso died uncondemned by his own hand, and whatsoever punishment fell upon his two sons was inflicted on them as the sons of a man who had been disloyal to the State, not as the sons of the murderer of Germanicus. It was therefore superfluous on the part of two Senators to propose that altars should be erected to Vengeance, and of another that thanks should be returned to certain members of the Imperial family because Germanicus had been avenged.
There is, in fact, absolutely no evidence that Germanicus was murdered, while there is abundant evidence that the relations between him and Piso, both personal and political, were exceedingly unsatisfactory, and that Piso was so injudicious as to endeavour to set aside his authority. Piso was by many years the older man of the two, he had had long experience of public affairs, had enjoyed the confidence of Augustus, and acquiesced very unwillingly in the arrangements which put Germanicus, a much younger man, over his head. It is quite possible that he had private instructions from Tiberius to give Germanicus the benefit of his experience in friendly fashion, and that he interpreted these instructions wrongly, believing them to amount to a declaration of his own independence of Germanicus, and he would be the more ready to believe this because he was touchy on the subject of his own dignity; but that he actually carried authority to thwart and annoy Germanicus is as improbable as that he had instructions to poison him. Tiberius was guilty of a mistake in not anticipating the friction that would necessarily arise between an older man and a younger man when the former was placed in subordination to somewhat indefinite powers wielded by the latter. If the two men had been left to settle their differences alone, there would probably have been little trouble, for Germanicus began with courtesy and forbearance, but the ladies insisted on taking an active part in the quarrel. Agrippina saw Livia written large all over Plancina, with whom she had doubtless enjoyed several preliminary skirmishes at Rome; and Plancina met her on her own field and fought her with her own weapons, for, reprehensible though Plancina’s military performances appeared in the eyes of a pattern Roman matron, Agrippina had herself set the fashion in Germany. The atmosphere of the East was a particularly unwholesome one for two ladies thus mutually breathing out threatenings and slaughters, and listening to tales depreciatory of one another. The East swarmed with sorcerers and necromancers, and supple intriguers of all kinds used to the internecine feuds of the ladies who lived in the palaces of their princes.
The most unfortunate result of the death of Germanicus was that it left Agrippina an embittered and vindictive woman. Even her husband had occasionally deprecated the violence of her temper. Time did nothing to cure her grievances, indeed the legend of her many sorrows seemed to grow steadily as the events receded into the distance, and she handed her quarrel on to her children with its vitality undiminished.
One possible solution of the part played by Piso, and of the difficulty of reconciling it with his last protestation of innocence, is that Plancina was actually in the confidence of Livia, from whom she held such a commission as Livia could give her to make arrangements desired by her patroness. The Oriental princes had learned to rely on secret influence rather than on open negotiations with Tiberius and the Senate; the stern impartiality of the Emperor drove them to subterranean manœuvres, and Livia was by no means disinclined to let it be understood that her influence was paramount. Thus while Piso as Governor of Syria was the properly constituted representative of Tiberius, his wife was the accredited plenipotentiary of the power behind the throne. The charges against Plancina were really charges against Livia, and the case which was hushed up was the case which would have exposed the unauthorized political intrigues of the Empress Dowager. Tiberius could either allow his mother’s interference with State affairs to be a subject of public inquiry, or he could allow Plancina to be tried on the frivolous charge of poisoning with the certainty that she would escape conviction. He preferred the less heroic course, with the result that both he and his mother were credited with having been concerned in a criminal conspiracy against a near relative.
The tradition repeated by Tacitus, that Piso was in possession of documents which would have established his innocence by demonstrating the complicity of Tiberius and Livia, and that he refrained from producing them on being assured of his safety by Sejanus, is not incompatible with this view of the case. Tiberius would certainly not have been involved, but instructions given by Livia to Plancina may very well have existed, and have led to those reversals of the policy of Germanicus which produced the ultimate quarrel. On this assumption the suicide of Piso becomes intelligible, he could not defend his grave political misconduct without exposing the still graver misconduct of the Empress Dowager, and when he saw that no other means of escape was open to him, he took a course which, to the Romans, did not seem to be devoid of heroism. Tiberius may have been weak in not dismissing his mother to an island, but he was certainly not responsible for the death of Piso, or concerned in a plot to poison Germanicus.