Acts 25:7

‘And when he was come, the Jews who had come down from Jerusalem stood round about him, bringing against him many and grievous charges which they could not prove,'

Present also in the court were the Jews who had come down from Jerusalem for the purpose, who stood around him bringing against Paul ‘many and grievous charges which they could not prove.' It was, however, a maxim of Roman justice, as of Jewish justice, that a man could not be convicted on accusation alone. There must be evidence and a case must be proved. And Festus was a just man.

We note that this is the third opportunity that Paul has had to speak and witness before prominent Jews. We may assume that not all were proof against his testimony. Even among these men some were being won for Christ.