John 18:28-29 (NASB)
28 Then they *led Jesus from Caiaphas into the Praetorium, and it was early; and they themselves did not enter into the Praetorium so that they would not be defiled, but might eat the Passover. 29 Therefore Pilate went out to them…
Y'shua’s trial before Pilot occurred during the early morning hours after the “Last Supper” was eaten. If at that time, the Jews were afraid of going into the Praetorium because they would be defiled and unable to eat the Passover, then there is no way that the Last Supper, which had been eaten the night before, could have been the Passover Seder. Furthermore, John records that while Y'shua was being crucified the day after the Last Supper was eaten:
John 19:31 (NASB)
… the Jews, because it was the day of preparation, so that the bodies would not remain on the cross on the Sabbath (for that Sabbath was a high day), asked Pilate that their legs might be broken, and that they might be taken away.
In context the phrase, "for that Sabbath was a high day", indicates that the Sabbath in question was Passover. Though some might argue that this passage refers to the weekly Sabbath, a weekly Sabbath would not be described as a "high day" unless it coincided with one of the Moedim, like Passover. Therefore, it is safe to assume that this passage indicates that the Jews wanted Y'shua's body removed before it was time to eat the Passover. Since the Last Supper was eaten at twilight the night before Y'shua's trial and crucifixion, the Last Supper could not have been the Passover Seder.
In my next post I will explore another reason that the Last Supper could not have been Passover.