The legitimacy of the call has been debated since it happened. Bills quarterback Ryan Fitzpatrick rolled out of the pocket to the right and heaved a pass off his back foot just before linebacker Brandon Spikes could put a hit on him. Barrett camped out in the front of the end zone before hauling in the interception.
However, it was called back due to a flag thrown on safety Sergio Brown, who got tangled up with David Nelson behind Barrett in the back of the end zone. The argument, from there, surrounded whether or not Brown deserved the flag after Nelson appeared to initiate contact. Yet, if Brown showed better awareness and turned his head toward the ball, he probably would have been fine.
That's not the point of contention in New England, though. Some defensive players were adamant that Spikes deflected the pass when it left Fitzpatrick's hand, based on the postgame film sessions they've done. If Spikes did deflect the ball, officials would not have been permitted to call pass interference on Brown, or anyone. Essentially, when a pass is tipped, defensive players are allowed to tackle every player on the field while the ball is still in the air.
It's not convincingly clear, one way or the other, from the television broadcast if Spikes got his hand on the ball. Tipped passes are also reviewable, so head coach Bill Belichick could have challenged the play if he wanted.
The play resulted in a 31-yard penalty that put the ball at the New England 1-yard line, and running back Fred Jackson scored on the next play to tie the game 24-24. On the very next offensive play, cornerback Drayton Florence returned a Tom Brady interception for a touchdown that gave the Bills a 31-24 advantage.
Clearly, the pass interference penalty served as one of the pivotal moments in the game, and the Patriots have questioned the legitimacy of the flag that turned the tide of the outcome.