I recently watched Silence of the Lambs (1991) and was wondering what Hannibal's mask actually does and why he needs it. When I first saw it, I thought it stopped him talking as people have been warned about what to say to Lecter. However, I was clearly wrong. Still trying to figure it out, I concluded that it must be to prevent Hannibal biting the Senator's face off. But if surely his restraints are enough to prevent him getting close enough to do that.
This doesn't look like someone who has enough range of movement to do that, even without the mask. So why do they give him it? Is it just a precaution?