It appears the Gospel of John was written by Nicodemus, who visited Yeshua, so making him a member of the Pharisee or High council.

There are many references that only he would have known about; some of these include the private conversation of him and Yeshua, the measurements of good brought for the burial, and then the many private Pharisee and high council conversations.

Here is an Article on many of the private Pharisee conversation points, that don't match the other gospels in terms of it being a disciples account, yet then that of Pharisee; of what looks like John Nicodemus (which can also be Nicolaitans, which is form of Nicholas).

Here is an Article on where some of the Gospel of John deliberately contradicts the Bible through out and Yeshua on many points.

With many points that appear false testimony, in like where The Christ was led to Pilate the testimonies don't match.

There are many more points that if gone over, which will show the whole of the Gospel of John, can not be trusted as testimony, when it contradicts Yeshua meaning and teachings, on so much!