Tractate Sanhedrin, Herbert Danby tr. , at sacred-texts.com
M.VII. 5. The blasphemer 2 is not guilty until he have expressly uttered the Name. According to R. Jehoshua, the son of Karha, the witnesses throughout are examined by means of pseudonyms: 3 for example " Jose strikes Jose." But when the trial is over the sentence is not carried out under a pseudonym: all are sent out of the room except the chief witness, and it is said to him: "Say expressly what you heard." He does so, whereupon the judges stand up and rend their clothes; 4 and they may not mend them again. The second witness then says, "I heard the same," and the third says, "I too heard the same."
98:2 See Lev. 24. 10 ff. According to the Talmud (cf. Yoma 39 b), the pronunciation of the Sacred Name was at one time known to all; but "from the time that Simon the Just died"--the customary expression for the beginning of the Hellenistic period--it was gradually forgotten.
98:3 The witnesses who had heard the blasphemy might not repeat the words, but made use of an arbitrary formula to describe the crime.
98:4 Cf. Mark 14. 63; Matt. 26. 65.