There is pretty good empirical evidence that Mark's gospel is not eyewitness testimony, in that he is confused about the geography of Palestine.
Mark says that, "Then Jesus left the vicinity of Tyre and went through Sidon, down to the sea of Galilee and into the region of the Decapolis." (Mark 7:31, NIV)
In Matthew 15, Matthew says the same thing.
How has the geography been confused?
Do you have evidence/proof that Jesus did not take this route that Mark and Matthew give account of?
If this is the only/best evidence you have against the Bible containing eyewitness testimony...You might want to re-evaluate.
Actually there is good solid scholarship that Mark wrote down Peter's eyewitness testimony. Since you are no theologian or bible scholar, you will have to provide evidence or refrain from those types of statements.