I've been a professor at BYU for some time now. Heard all the excuses. I finally determined that the best way to approach this was to assume that the student is being honest with me and to bend over backward to help them. My experience has been that 90% of the time the student was being honest. If it ends up that they weren't being honest then it is on their heads. Dishonesty in one class is generally a sign of issues across the board. When it comes time for grades I find that those that are trying to game the system still don't do a great job and don't tend to skew the curve much, if at all. Just my two cents.