Board Thread:Legitimate Canon Questions/@comment-68.150.73.87-20140709011459/@comment-4091815-20140709011654

Scott's arms were pinned behind him - if he hadn't used his teeth, Liam would have fallen to his death.

Had he retracted his fangs, he would not have been able to get a good grip and Liam would have fallen to his death.

In other words - had Scott not bitten - Liam would be dead.