In 74 B.C. he accused his stepfather Statius Albius Oppianicus of an attempt to poison him;.

Oppianicus and two others were condemned, and some years later Oppianicus died in exile.

In 66, Sassia induced her stepson Oppianicus to charge Cluentius with having caused the elder Oppianicus to be poisoned while in exile.

His efforts are chiefly devoted to proving that the condemnation of the elder Oppianicus was just and in no way the result of the jury having been bribed by Cluentius; only a small portion of the end of the speech deals with the specific charge.

But even if it could be shown that Cluentius had bribed the jurymen, this did not prove that he had poisoned Oppianicus, although it supplied a sufficient reason for wishing to get him out of the way.