Many books and authorities on the subject often suggest that it is the teacher's responsibility to tend to cheating. But does 100% of the responsibility for preventing cheating fall on the shoulders of the instructor?
Your perceptions of the problem, and your moral and ethical makeup are going to determine how far you go to prevent cheating in your class or program. They also will help determine whether you will enforce the rules and follow the guidelines for disciplinary action when you believe someone has cheated in your class.
Where are you on this responsibility-for-preventing-cheating continuum?