Augustus made a law that the slaves of those who conspired
against his person should be sold to the public, that they might depose
against their master.
[44]
Nothing ought to be neglected which may
contribute to the discovery of a heinous crime; it is natural,
therefore, that in a government where there are slaves they should be
allowed to inform; but they ought not to be admitted as witnesses.
Vindex discovered the conspiracy that had been formed in favour of
Tarquin; but he was not admitted a witness against the children of
Brutus. It was right to give liberty to a person who had rendered so
great a service to his country; but it was not given him with a view of
enabling him to render this service.
Hence the Emperor Tacitus ordained that slaves should not be
admitted as witnesses against their masters, even in the case of high
treason:
[45]
a law which was not inserted in Justinian's compilation.
