en_tn/mat/26/65.md

the high priest tore his clothes

Tearing clothing was a sign of anger and sadness. (See: rc://en/ta/man/translate/translate-symaction)

He has spoken blasphemy

The reason the high priest called Jesus' statement blasphemy is probably that he understood Jesus' words in Matthew 26:64 as a claim to be equal with God. (See: rc://en/ta/man/translate/figs-explicit)

Why do we still need witnesses?

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. Alternate translation: "We do not need to hear from any more witnesses!" (See: rc://en/ta/man/translate/figs-rquestion)

now you have heard

Here "you" is plural and refers to the members of the council. (See: rc://en/ta/man/translate/figs-you)