Top 10 Ways that Mel's Passion Isn't As It Was, Number 7...

7. Roman soldiers were present when Jesus was arrested.

From the MSNBC article Who Killed Jesus?:

In an ensuing scene, Mary Magdalene calls for help from Roman soldiers as Jesus is taken indoors to be interrogated by the priests. "They've arrested him," she cries. A Temple policeman intervenes, tells the Romans "she's crazy" and assures them that Jesus "broke the Temple laws, that's all." When word of the trouble reaches Pilate, he is told, "There is trouble within the walls. Caiaphas had some prophet arrested." It is true that the Temple leaders had no use for Jesus, but these lines of dialogue—which, taken together, suggest Jewish control over the situation—are not found in the Gospels.
Compare this to John 18:3:
So Judas brought a detachment of soldiers together with police from the chief priests and Pharisees, and they came there with lanterns and torches and weapons.

The Greek word "detachment" is a specific part of the Roman army. Yet Mr. Gibson portrays the Roman soldiers as completely unaware of the Gethsemane arrest. This part of the movie isn't history; it isn't even biblical.