Stephen is obviously facing a hostile audience, a kangaroo court. The verdict has already been decided on, but formalities must be observed. Stephen addresses his hearers in Greek, and quotes from the Greek translation of the Old Testament, the Septuagint. He is obviously a gifted speaker, he engages his audience and holds their attention with one tale of betrayal after another. After all, treason is the reason he's standing before them that day! And there are so many accounts of people who were betrayed by family (like Joseph) and tribe (like Moses) who nevertheless ended up having in the last laugh.
Finally, in a brilliant turn of phrase that turns the tables, Stephen makes it plain who the real traitors are:
Act 7:51 "Ey dik kafalılar, yürekleri ve kulakları sünnet edilmemiş olanlar! Siz tıpkı atalarınıza benziyorsunuz, her zaman Kutsal Ruh'a karşı direniyorsunuz.A key term here is dik kafalılar: the obstinate, pigheaded, bull headed, headstrong folks. You are like your fathers, always resisting the Holy Spirit. Your fathers, the prophets, which of them did they not persecute? Melekler aracılığıyla -- angels by the means of. buyrulan Yasa'yı alıp da buna uymayan the law you received, but have not kept.
Act 7:52,53 Atalarınız peygamberlerin hangisine zulmetmediler ki? Adil Olan'ın geleceğini önceden bildirenleri de öldürdüler. Melekler aracılığıyla buyrulan Yasa'yı alıp da buna uymayan sizler, şimdi de Adil Olan'a ihanet edip O'nu katlettiniz!"
Judges hate it when the defendant puts them on trial, and convicts them so convincingly. We know that Stephen's defense made a powerful impression on at least one hearer, since he remembered the details so clearly, and long enough to convey the whole story to Luke.
 In synagogues throughout the Roman Empire, when non-Jewish people came to worship the God of Israel, they addressed the Lord as the "God of their fathers."