<p>I think you do have to take the severity into consideration. I think I would feel differently about my ethical duty to report if I witnessed a murder as opposed to witnessing somebody failing to come to a full stop at a stop sign.</p>
<p>I think this is an interesting question only if there isn’t an honor code that requires you to report. I think considerations would include how serious the offense is, how likely it is to harm other people, etc. Thus, for example, you might want to report somebody who was cheating in order to get a specific prize that only one person can get, but not somebody who is cheating on one homework assignment in a class with 200 other students.</p>