ἐκμαρτῠρ-έω · ekmartyr-eō — LSJ
to bear witness to a thing, c. acc., φόνον A. Eu. 461; ἐκμαρτύρησον..τό μʼ εἰδέναι Id. Ag. 1196; εἰς πολλούς before many persons, Aeschin. 1.107:—Pass., Str. 12.8.6.
make depositions out of court, Is. 3.21, Test. ap. D. 35.20, Aeschin. 2.19.