Ggtkuk

I'm assuming from my experience with Canadian academia that this is a test that is taken in class, you turn it in at the end of the period, and then your professor either gives them back, graded, or allows you to come to their office and see your graded test.

Before you meet with the professor, you should find out whether your friend should have had a copy of the exam. Yes, if you saw a copy of an exam that was not released after the exam, it could be considered a form of cheating and you might get in trouble.

If it was released to the class (or is a take home exam everyone had a chance to see), then there is no issue.

To be clear, I sincerely doubt you will get in trouble here. What you did is reasonable and expected, but at the very least, you should be prepared to explain the situation and know where the test came from. Maybe the professor would like to know who is leaking their tests.

I have had classes where professors kept their tests well-hidden enough that if someone had a copy, I would immediately have suspected them of wrongdoing. Without more details, it's impossible to know how your situation fits in.

While the other answers provide good advice how to handle the situation in a polite and diplomatic manner, we should nevertheless get the actual questions straight:

Is having access to past exams cheating and, if yes, could it be proven just by a good grade?

(1) No, having access to past exams does not constitute by any means a case of cheating.

(2) No, an (unusually) good grade cannot be taken as a proof of cheating.

The following describes the legal situation in Germany, where cheating in an exam actually has a pretty narrow definition: It is constituted by unauthorised behaviour during the exam, such as taking unapproved material into the exam, talking or communicating with another student, and so on – the exact cases of unauthorised behaviour are defined by your institution. However, you have to be caught in flagranti or by clear proof of an action you did during that exam.

The situation may be different in other legal systems.

In the UK, the norm (insofar as one can say there is any norm -- each university has its own rules and procedures) is for past papers to be available, and for the onus to be on the examiner(s) to devise a new paper for each examination session. The exception might be if you had to sign something saying explicitly that you will keep the material you see/use confidential.

In the university where I did my undergraduate degree, the past papers were available as bound volumes in the library reference sections, and we were at liberty to photocopy or transcribe any part of these volumes. Towards the end of my undergraduate degree, an official initiative was started by the university to also make the past papers available for download from the web. In addition, examiners' reports, giving general (anonymised) feedback on the strengths and weaknesses of the cohort that sat the examination, were similarly available for perusal.

In short, past papers were not only considered fair game, but we were actively encouraged to look at them and use them for practice purposes. Our tutors would set mock examinations using past questions, and we would discuss in detail approaches, strengths, and weaknesses. Sometimes, tutors would re-use materials from year to year, but such re-use would never occur for anything that counts towards an official assessment, unless the material is a very generic starting-point, made known to the students at the beginning of the academic year, for a coursework assignment.

When I worked at University our professor used to do this to ~10 people each semester.
He usually picked some of the best results (just to be sure), but mostly people who handed in assignments way above their expected level.

He showed them one of their answers, and asked them to elaborate.
If people could give some background information, their thinking process, etc, the whole thing took less than 5 minutes, and people just left with their graded assignment.
People who cheated could usually not tell him anything except what they had written and he failed them.

So: If the exam had the same questions as last year, and you got the answers from your friend you might be in trouble. If you genuinely learned for the exam and the result represents your knowledge about the topic you should have nothing to worry about.

Absolutely not. Any work that any professor does is something that can and should be studied. He's the professional and it is his responsibility to change the questions if he does not intend for them to be known in advance.

You just said that you think the exam was made public. Why would be using something that the teacher made public be considered cheating?

I had a teacher at the university whose exams were 80% a combination of old exams and 20% new questions. My university had a very strict rule where all teachers were required to make their past exams public. Most subjects even had them for download at the e-campus.

This guy once went into a public rant about how everyone passed his subject (this was unusual, as the rate of passing for most subjects was around 30%) and the unanimous response from the university was to put some effort on the exams.

If the exam is public and the teacher doesn't put any effort into making a new exam, why is you studying from the material considered cheating? Seems to me like your dilemma lies in the fact that the rest of the students didn't use the exam to study, and well, that's on them for not taking advantage of all the studying material.

When I was in college studying electrical engineering, professors regularly made the previous year's exam available at the local copy center for us to purchase as a study aid. Some would also offer extra help sessions where you could come in and discuss the exam with a TA, etc. One of my friends was in a frat and he would regularly show up with copies of the exam from several previous years. We would study all night, passing each exam around until all of us could do every question on every exam. Not only was this NOT cheating but a solid study tactic because many of the questions were similar to actual exam questions.

As some have stated, you should have looked into whether or not your friend was supposed to have the exam or not. Some professors collect them afterwards and don't allow the actual exam to be had outside of the class room. If that was the case, I don't think you cheated since you didn't have fore knowledge of the actual exam but one could argue that it was unethical. Either way, I would be honest with the professor if he asks about your study practices and how you achieved such a grade.

Depends on your testing regulations.

The ones at my university (and department) state that professors CAN NOT stop or punish you for 1) photographing it when examining it (i don't know the english word for this, but we can check our stuff for correction errors after the grades are published) and 2) distributing said photographs.

In Fact, some professors even share PDFs of the last exam, to make it fair for everyone.