I am a final-year PhD student in Canada studying cybersecurity. During my PhD, I did not have very good supervision. I told them I wanted to defend soon. However, one of my supervisors keeps on telling me: “Don’t rush, you may fail”.

I got one first-author paper in IEEE Transactions and 3 medium level first-author conferences accepted. How can I fail? Is it possible? Has anyone ever failed the PhD defense?

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    – Bryan Krause
    Commented Jan 13, 2023 at 16:47

8 Answers 8


There are definitely fails in PhD defenses. It may depend on the specific system and I don't know about Canada, but I know of a number of them in the UK, where the candidate was asked to rework and come back in a year or so. Also PhD examiners in the UK don't have to accept a thesis just because there are publications. I do think some published material shouldn't have been accepted, and not everything I have seen published is in my view acceptable at PhD level.

  • 4
    I'd say that "major revisions" are not a fail necesarily. If you are told to work a bit more on it, yeah you fail as you don't get a PhD, but its not fail as "bye no PhD for you ever". Commented Jan 13, 2023 at 11:29
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    @AnderBiguri That's a fair enough objection to my use of terminology, however if you plan to apply/go for a postdoc or anything you need a PhD for directly after your defense, the immediate practical consequences are those of a fail. Commented Jan 13, 2023 at 11:38
  • Totally agree with that :) Commented Jan 13, 2023 at 11:42
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    yep, I remember an English student at Oxford who had published an entire book with Springer and was failed, which sounded like a real scandal to my ears. A friend of mine at Cambridge, was asked to completely rewrite his thesis, in Finance, spent a year doing it, sent the revision, did not hear from anyone for months, when he finally contacted them they said "Oh you passed last year". Nightmare.
    – PatrickT
    Commented Jan 13, 2023 at 19:16
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    @Tom There is some variation, also within the UK. I have seen both cases, where the viva had to be repeated, and where people were just told upon resubmission that they had passed now, even with major corrections. I don't remember exactly anymore but chances are I have even seen a form in which examiners could choose between these options (on top of minor corrections). Commented Jan 14, 2023 at 11:04

Your supervisor is aware of expectations for a PhD program. Their role is to help you understand these expectations and develop your PhD work to this standard.

Having one IEEE Trans publication and a few proceedings is good, but not necessarily indicative that your work meets the criteria of a PhD award. Normally, PhD dissertation is a major piece of academic research, which can be compared to a manuscript (a book). A journal paper is a more scoped contribution compared roughly to one chapter of your PhD thesis. Having one journal paper published does not guarantee you a PhD. I am aware of some candidates with 5+ journal publications, who failed their defence because they rushed and did not write an adequate PhD dissertation. It definitely happens.

Having a postdoc offer before you completed your PhD is a good sign that your work is interesting and promising. However, if your postdoc offer is conditional on you completing the PhD successfully, you still have to complete your PhD. Seeing your advisor as an obstacle is not constructive or helpful. Once again, they are trying to help you, and you should see their expertise as a resource.

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    Everything here is correct, but I'll just caution that 'your supervisor is aware of expectations for a PhD program' does not imply that supervisors have a 100% track record of being right when they predict a fail. Commented Jan 12, 2023 at 20:30
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    @DanielHatton True. But they hedged their bets: "you may fail" is always true.
    – PatrickT
    Commented Jan 13, 2023 at 19:17
  • This is mostly good but "they are trying to help you" is not always true. Commented Jan 14, 2023 at 22:34

Why PhD Defenses fail rarely

The main reason why PhD defenses fail rarely is that the process is structured so that in general people attempt their defense only when they are almost certain to pass. If there are any issues and objections, there is a strong preference to have them resolved before a defense, not have them be raised during a rejecting vote in the defense process. No one wants to waste all the formal process effort on a failed attempt, so supervisors and committees will know that someone is likely to fail and strongly advise them to not make the attempt and postpone it, so in general a failure should happen only if the student has been warned that they are likely to fail and disregards this advice to make the attempt anyway. This sounds suspiciously similar to what you are describing.

  • This answer could be seen as slightly misleading. OP is in a situation where they have been warned by the supervisor that they could fail the PhD if they submit with the current results. In that situation, the chances of actually failing the PhD are much higher than in the average case. Commented Jan 13, 2023 at 13:46
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    @lighthousekeeper that's exactly what the answer is saying‽ Commented Jan 13, 2023 at 14:33
  • +1 for speaking to this specific case for the OP. This is probably the most useful answer to pay attention to. Maybe add some whitespace to guide readers?
    – Mike M
    Commented Jan 13, 2023 at 22:07

Yes it is possible to fail a PhD defence and it does happen. Thankfully this is rare.

I’m not in CS so I cannot compare with your peers but you should not make the error of thinking that you need so many publications to get a degree.

If anything, compare a situation where you have x publications as a single author with a situation where you have x publications with many co-authors. Obviously your intellectual contribution to each publication matters; your supervisors and members of your PhD committee can decide you have not done enough even if you have 2x publications because your contribution to each publication has been minimal. I want to emphasize I’m not talking about writing codes or some other such tasks: a PhD is a research degree so your advisor needs to convince your committee and eventually the external examiner that you have made significant and novel contributions to these publications.

I have heard of students failing at the defence stage. This is not pleasant, and it’s a situation everyone wants to avoid. It often (but not always) happens because the candidate is rushed by external events - some visa issue, some family matter, whatever.

In most systems I know, candidates will first go through a sort of “internal defence”, where the student may have to present their work to the committee, or there is some big committee meeting where the final draft of the thesis is evaluated before the thesis is sent to the external examiner. Nobody wants the student to fail so having the committee on board minimizes but does not eliminate the risk of failures. If the thesis is marginal and some committee members still have issue, but the thesis goes out anyways, there could be trouble at the defence with the external examiner.

If you think you have done enough but your advisor does not agree, it’s time to have a frank discussion with your supervisory committee to sort things out, and establish clear milestones for the completion of your degree.


The reason it is rare to fail a Ph.D. defense is that supervisors make sure nobody defends until they are ready. Don't push to be the exception.


Good answers already, but I think this might also be relevant.

Have you found your institution's academic regulations relating to research degrees? If not, you should. They might be a boring read but they should lay out the exact procedure and requirements for a PhD assessment as well as all the possible outcomes. There will be "failed" outcomes in the regulations. Sadly there will also be stories of students who have failed (even with publications). There might be resit opportunities, too. The regulations might also detail the appeals process if you do fail.

There is some debate in the comments here as to whether "major revisions" are considered a fail or not. The short answer is that depends on your institution's academic regulations.

One thing that the academic regulations are very unlikely to say is "1 good journal + 3 medium conferences = pass", so although your chances of passing are good, your chances of failing are unlikely to be zero.


From reading your other question, your supervisor isn't really saying that they think it's likely that you fail.

I need to submit one paper to a journal and write one conference paper, then I am ready to write my thesis.

I got a postdoc position in a great research lab. The tentative start date is the beginning of May. They asked for a letter from my supervisor, stating that I am going to defend before the beginning of May. However, my supervisor keeps on telling me he can only state that I can submit my thesis before that date. He wrote a letter for that.

Your current timeline has you starting, finishing, submitting, and defending your thesis in less than 4 months (really more like 3 months), with your defense being sometime in late April. Even if you and your supervisor do everything perfectly there are still a lot of outside factors that can impact that, the biggest one being when can/will your committee get together to hear your defense. Your timeline is so tight that if you submit your thesis and the committee takes a week to review it and then says we want some minor changes, we'll be able to review those changes in another week... What are you going to do? Or if one person can only meet on Wednesday and another person is unavailable on Wednesday so they have to schedule your defense for a week later? (Or two, or three...)

If you submit your thesis but don't have time to do the changes then it's possible that you could fail. It's even more likely that you don't fail but you don't pass your defense on your timeline. Your supervisor is (wisely) unwilling to commit to other people doing things that are outside of your control.


If your advisor says "it's time to get ready for your defense", your odds of passing are extremely high. If you try to defend against your advisor's will, that's a different story.

I would suggest you talk with your advisor about why they think you are not ready. It could be that they are not happy with your work and need more. It could be that they think you should take as much of the free study time you have in grad school and make the most of it: trust me, you will miss this aspect later in life!

If you believe you are being treated unfairly by your advisor in this situation, I would suggest you discuss with the chair.

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