The reason the high priest called Jesus' statement blasphemy is probably that he understood Jesus' words in [Matthew 26:64](./64.md) as a claim to be equal with God. (See: [[rc://en/ta/man/translate/figs-explicit]])
The high priest uses this question to emphasize that he and the members of the council do not need to hear from any more witnesses. AT: "We do not need to hear from any more witnesses!" (See: [[rc://en/ta/man/translate/figs-rquestion]])