Firing on the Canon
The Da Vinci Code also states that Constantine suppressed all documents about Jesus other than those found in our current New Testament canon (recognized by the church as authentic eyewitness reports of the apostles). It further asserts that the New Testament accounts were altered by Constantine and the bishops to reinvent Jesus. Another key element of The Da Vinci Code conspiracy is that the four New Testament Gospels were cherry-picked from a total of "more than 80 gospels," most of which were supposedly suppressed by Constantine.5
There are two central issues here, and we need to address both. The first is whether Constantine altered or biased the selection of the New Testament books. The second is whether he barred documents that should have been included in the Bible.
Regarding the first issue, letters and documents written by second century church leaders and heretics alike confirm the wide usage of the New Testament books. Nearly 200 years before Constantine convened the Council of Nicaea, the heretic Marcion listed 11 of the 27 New Testament books as being the authentic writings of the apostles.
And about the same time, another heretic, Valentinus, alludes to a wide variety of New Testament themes and passages. Since these two heretics were opponents of the early church leadership, they were not writing just what the bishops wanted. Yet, like the early church, they still referred to the same New Testament books we read today.
So, if the New Testament was already widely in use 200 years before Constantine and the Council of Nicaea, how could the emperor have invented or altered it? By that time the church was widespread and encompassed hundreds of thousands if not millions of believers, all of whom were familiar with the New Testament accounts.
In his book The Da Vinci Deception, an analysis of The Da Vinci Code, Dr. Erwin Lutzer remarks,
"Constantine did not decide which books would be in the canon; indeed, the topic of the canon did not even come up at the Council of Nicaea. By that time the early church was reading a canon of books it had determined was the Word of God two hundred years earlier."6
Although the official canon was still years from being finalized, the New Testament of today was deemed authentic more than two centuries before Nicaea.
http://y-jesus.com/monalisa_5.php