In fact the source of the accusations against him were certain Jews from Asia. It was they who, as his original accusers, should have been there if they really had anything to accuse him of (that was the law). But they were not there. The whole case was trumped up.
Roman law in fact imposed heavy penalties on accusers who abandoned their charges (destitutio), thus their absence suggested that they recognised that they had nothing against him that would stand up in a Roman court of law