Defer exam?

<p>I am feeling and I don't think that I will be able to write one of my finals. I'm considering applying for a deferral but I am worried because I have heard that they sometimes reject deferral applications and students end up with 0's on their final exams.
I had intended on seeing a doctor the morning of the exam and bringing in the note to whomever dealt with exam deferrals on the next day.
Does anyone know what the process is for exam deferrals? Does the Dean investigate each student's request? Does the professor himself/herself have any role in this process?
Thanks.</p>