# the high priest tore his clothes

Tearing clothing was a sign of anger and sadness. 

# He has spoken blasphemy

The reason the high priest called Jesus's statement blasphemy is probably that he understood Jesus's words in Matthew 26:64 as a claim to be equal with God.

# Why do we still need witnesses?

"We do not need to hear from any more witnesses!" 

# now you have heard

Here "you" is plural and refers to the members of the council.