There was suspicion at the time - which is supported by many modern historians - that Piso was a fall guy.Two thousand years ago today...
'On the 10th of December, in the year 20 AD, the most spectacular trial of the early principate ended. The defendant was charged with nothing less than the murder in Syria of Germanicus, adopted son and declared heir of the emperor Tiberius. The accusation was made against Cn. Calpurnius Piso and his wife Plancina, who had both been in Syria at the same time as Germanicus.
'Germanicus’ friends laid a charge of murder, but they were unable to prove this during the trial. Nevertheless, the accusation did not collapse, because a number of further, very serious charges were brought. Above all, Piso was accused of inciting Roman troops to fight each other in Syria, in other words, of instigating civil conflict. The accused saw no chance of getting off free. After the fifth day of the trial, he took the only way out, and committed suicide. He was found in his bedroom, with his throat cut, the following morning. The trial nevertheless continued: after two more days, the senate gave their verdict: Piso would have been sentenced to death, if he had not forestalled them. But his wife Plancina, and his son Marcus, who had been accused with him, were set free, because Tiberius, and especially his mother Livia, intervened on their behalf.'
Tsk-tsk, Tiberius! How non-CF-ish!
Germanicus was hugely popular with the people, the Senate and, most importantly, the Army. Not only was he good looking and charming, but he was an enormously successful general who drew frequently comparison to Caesar and even Alexander the Great. Tiberius, on the other hand, had had a mediocre military career and had all the charisma of a plow horse. The notoriously paranoid Tiberius may have feared that Germanicus would overthrow him. Piso, whose family had always been allies of the Julio-Claudians, may have been ordered to kill Germanicus or was set up to take the fall. He may have committed suicide on condition that his family was protected.
Tiberius wasn't so kind to Germanicus' family. His widow, Agrippina was exiled to an island where she was starved to death, as was his son Drusus. His other son, Nero (not to be confused with the later emperor, who was Germanicus' grandson) committed suicide rather be executed on a trumped up charge of treason. His remaining son, Gaius, nicknamed Caligula, remained with Tiberius on the island of Capri, where the Empreror preferred to spend his time engaging in perverse pleasures that may have included crucifixions and did include having people thrown off the cliffs. He also groomed his grandson to succeed him.