A few problems here - the sanhedrin stopped capital punishment before 30AD and, from what I'm reading, Stephen was supposedly killed after that. Also, what one has to say under Jewish law to be considered a blasphemer is nothing like what Stephen seems to say. And the punishment of stoning requires pushing the naked criminal off of high place, not throw rocks at him.
And thou shalt speak unto the children of Israel, saying: Whosoever curseth his God shall bear his sin. And he that blasphemeth the name of the Lord, he shall surely be put to death; all the congregation shall certainly
stone him; as well the stranger, as the home-born, when he blasphemeth the Name, shall be put to death. ... And Moses spoke to the children of Israel, and they brought forth him that had cursed out of the camp, and
stoned him with stones. And the children of Israel did as the Lord commanded Moses. - Leviticus 24: 15-23
If there be found in the midst of thee, within any of thy gates which the Lord thy God giveth thee, man or woman, that doeth that which is evil in the sight of the Lord thy God, in transgressing His covenant, and hath gone and served other gods, and worshipped them, or the sun, or the moon, or any of the host of heaven, which I have commanded not; and it be told thee, and thou hear it, then shalt thou inquire diligently, and, behold, if it be true, and the thing certain, that such abomination is wrought in Israel; then shalt thou bring forth that man or that woman, who have done this evil thing, unto thy gates, even the man or the woman; and thou shalt
stone them with stones, that they die. - Deuteronomy 17:2-5
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Stephen died ca. 34 CE; Jesus died ca. 33 CE. They were contemporaries.