[Note: adding another answer separately from my already existing one to address a different part of the question concerning the reliability of a facebook screenshot as evidence]
From the rumours going around, the evidence gathered is a screenshot of a facebook conversation, is this even enough evidence?
There has been a lot of discussion in the other answers and comments about the possibility of faking Facebook screenshots, which ostensibly calls into question the validity of using the screenshot as evidence. I find this premise entirely laughable, for the following reasons:
A motive for this outlandish forgery is completely missing. Why on earth would a faculty member even consider doing something so extreme as planting fake evidence to frame an innocent student of academic misconduct (but then sabotaging this daring act of forgery by forging only a relatively mild and controversial kind of offense that isn't even perceived as misconduct by some of the participants here)? We are talking about a final exam for a university course, not international espionage. Thus, the a priori likelihood of forgery, unless perhaps it is accompanied by prior evidence that the faculty member in question is some kind of psychopath, seems close to 0 to me.
The discussions in the other answers focus on legalistic arguments (see, e.g., RoboKaren's answer and her interesting, but amusingly irrelevant, discussion of the doctrine of the fruit of the poisonous tree) and seem to revolve around the question of whether the facebook conversation screenshots would be admissible in a court of law in the event of a criminal prosecution. Well, people, I'm afraid you have all watched one too many episodes of Law and Order. An academic misconduct hearing is decidedly not a criminal court of law, and the standard of evidence required to find a student guilty of misconduct is much lower than "beyond reasonable doubt". From my experience serving on my university's Campus Judicial Board and sitting on academic misconduct hearing panels, usually in U.S. universities (but this may depend on the university and jurisdiction) the standard that is applied is that of "preponderance of the evidence", i.e., a more than 50% likelihood of guilt. Given my argument above about the implausibility of forgery playing a role here, this would be an easy standard to meet.
To summarize, in the context of an academic misconduct investigation, the facebook screenshot would be just as good and acceptable a piece of evidence as a video recording of the student talking to their friends. So yes, it is (more than) enough evidence.