Quite possibly, I am not a historian. My understanding is as such: The historical content of the gospels places the earliest date (Mark) to sometime after the Jewish uprisings in which the Romans destroyed the temple in Jerusalem in 70 AD. Other gospels were most likely written after 93 AD due to references to other material (Josephus' Antiquities of the Jews,) with known publication dates. John was likely written in the early 2nd century and not by one person.
The persons who wrote the Gospels were also not familiar with the local geography of Palestine having misplaced cities and events that had to be later corrected.
In addition, the persons who wrote the gospels were highly proficient in Greek which would not be usual for a Jew from Palestine. Also, there are references to the old testaments that were observably derived from the Greek translations of the old testaments instead of the original Hebrew versions that would have been contemporary to Palestine at the time. It simply would make no sense for any of the original apostles to reference a Greek translation of the Hebrew bible of their own Jewish culture.
And all we have at present are copies of copies and no originals.
All of these facts together place further distance between the writers of the Gospels and any eye witness accounts of events.
I would be inrested any updated information.