Ye have sent (humeis apestalkate). Emphatic use of humeis (ye) and perfect active indicative of apostellō, official and permanent fact and so the witness of the Baptist has to be recognized as trustworthy by the Sanhedrin. The reference is to the committee in Joh 1:19-28.
He hath borne witness (memarturēken). Perfect active indicative of martureō showing the permanent and abiding value of John’s testimony to Christ as in Joh 1:34; Joh 3:26; Joh 5:37. So also Joh 19:35 of the testimony concerning Christ’s death. This was the purpose of the Baptist’s mission (Joh 1:7).