Plato, Laws 937b

μόνον ἐξέστω μαρτυρεῖν καὶ συνηγορεῖν, ἐὰν ἐγγυητὴν ἀξιόχρεων ἦ μὴν μενεῖν καταστήσῃ μέχρι δίκης, ἐὰν ἐπισκηφθῇ τὰ ψευδῆ μαρτυρῆσαι. ἐπισκήπτεσθαι δὲ τῶν ἀντιδίκων ἑκάτερον ὅλῃ τῇ μαρτυρίᾳ καὶ μέρει, ἐὰν τὰ ψευδῆ φῇ τινα μεμαρτυρηκέναι, πρὶν τὴν δίκην διακεκρίσθαι· τὰς δʼ ἐπισκήψεις τὰς ἀρχὰς φυλάττειν κατασεσημασμένας ὑπʼ ἀμφοῖν, καὶ παρέχειν εἰς τὴν τῶν ψευδομαρτυριῶν διάκρισιν. ἐὰν δέ

she shall only be allowed to give evidence. A male or female slave and a child shall be allowed to give evidence and support a plea in murder cases only, provided that they furnish a substantial security that, if their evidence be denounced as false, they will remain until the trial. Either of the opposing parties in a suit may denounce all or part of the evidence, provided that he claims that false witness has been given before the action is finally decided; and the magistrates shall keep the denunciations, when they have been sealed by both parties, and shall produce them at the trial for false witness.