This is something I don't understand: how come many degrees have been revoked due to plagiarism after approval if Turnitin and many other software against plagiarism exist?

For example, there was a case in my country where a politician got his degree revoked when it was found that he copied from other student's thesis, the thesis of that student was in her college repository, how come anti plagiarism software didn't detect the fraud before approval?

  • 1
    You say "many degrees have been revoked". I doubt that is true, actually. A few. The case you cite is at least partly due to the prominence of the politician. Had it been an ordinary, hence invisible, person, I doubt that anyone would have checked and if they did and found the same thing, would probably let it go as "not worth the hassle". I think the case in question was pretty blatant and the person was flaunting his degree as evidence of greatness. Yes?
    – Buffy
    Commented Feb 3, 2019 at 0:25
  • 3
    Anti plagiarism software is a recent invention; actually software is a recent invention; heck, writing your thesis on anything other than a typewriter is a recent invention. Commented Feb 3, 2019 at 14:31
  • Software like turnitin also is pretty useless for mathematics too. Commented Jul 25, 2020 at 8:58
  • What does this question have to do with politicians? I think nothing. Commented Jul 25, 2020 at 12:18

4 Answers 4


Actually, it is not just politicians. The media only report on politicians, though. I work with the VroniPlag Wiki academic group, there are over 200 published documentations of plagiarism, and many of these degrees have been revoked: http://de.vroniplag.wikia.com/wiki/%C3%9Cbersicht (sorry, in German, but you get the gist).

As others have noted, Turnitin and other systems are just a tool, not a litmus test for plagiarism. They can only find what their algorithms can find in the database they have been able to populate. There are very many false positives and even more false negatives. The reports are very difficult to interpret, to boot.

For your particular question, I know from my work testing plagiarism detection systems that very many repositories of dissertations are not indexed by the software. One reason is that they are very difficult to traverse (and each has a different structure). There only tend to be the dissertations stored in the databases that have previously been checked. So in your case, if the student's thesis A was not checked, it was not in the database when B was potentially checked. But if a human reader sees that the topic is the same and then compare's thesis A with thesis B, they can quickly see and document the overlap. And of course, not all theses are checked, for various reasons, not all of which are academic in nature.

If you want to know more about the work that goes into documenting plagiarism in (oldish) theses, I blogged about that ages ago: https://copy-shake-paste.blogspot.com/2012/10/how-to-find-plagiarism-in-dissertations.html (in English).


Turnitin and other tools are mainly (exclusively) Internet based plagiarism tools. They check if a submitted piece of work contains passages that match those found elsewhere on the Internet or previously submitted to the tool.

There are many sources that are not on the internet and created before such tools and technology existed. Any plagiarism from those would not be detected by things like TurnitIn.

In particular the historical (i.e. before 21st century) thesis archives of most university libraries have not yet been digitised and made Internet browsable. If someone just copied one and handed it in as theirs, then the only protection from plagiarism is the knowledge and experience of the examination panel (who would be expected to be familiar with prior works).

A further reason might be that not all institutions require the submission of a thesis in machine readable form. You can only use Turnitin on document files like word or PDF. You cannot (easily) use such tools for physical paper copies of a thesis. Some universities might still take submission as a bound book making detection mechanically difficult. Further, they might just not subscribe to TurnItIn et.al. as they might be too expensive and rely on the old human element instead.

This is why, when such blatant copying is later discovered a degree might be revoked.

  • But I saw news that the original files are documents already in the web. How come plagiarism wasnt detected there on time? Commented Feb 2, 2019 at 22:17
  • 1
    @CarlosVarasTello If you are asking about a particular case you should have given more details, then someone could answer about that case in particular. There are many reasons why this might be so . Commented Feb 2, 2019 at 22:20
  • @CarlosVarasTello Answer updated to explain. Commented Feb 2, 2019 at 22:48
  • Services like Turnitin weren't available twenty years ago, even though theses from that era are often available online. Now that services like this exist, some people have taken to checking old these for plagiarism. Commented Feb 2, 2019 at 23:00
  • @BrianBorchers, and, I'd guess that they are finding parallel work that only looks like plagiarism but isn't, since back in the old days it was harder to find parallel work as it took longer to disseminate. Some dissertations wouldn't appear in the scientific literature for a few years after degrees were awarded.
    – Buffy
    Commented Feb 3, 2019 at 1:10

Turnitin is not a fire and forget tool, it requires significant human effort to go through the results and separate serious plagiarism from sloppiness from outright false positives. Doing it retroactively is even harder because you have to carefully check who copied who.

Also turnitin only looks for straight text copying, it doesn't look for the (IMO more serious) stealing of ideas.

And of course it's not omnipresent either, lots of stuff (even stuff that is online) isn't in their database.

For normal students noone cares enough to do the work of trudging through old thesis looking for plagarism, famous politicians and other people who lots of people have a grudge against are another matter.


It is a controversial question (especially, if it refers to politicians). The issue of academic misconduct is an everlasting problem. A lot of famous people and thought leaders (including Martin Luther King) plagiarised and used other people’s ideas in their papers. Previously it was:

  1. hard to detect plagiarism, as there were no such innovative technologies and software;
  2. the requirements were not so strict towards the authenticity of the papers. With the lapse of time plagiarism detection software was developed. Nowadays, no software can detect any type of cheating and has access to all the repositories available. It is just impossible as there is no common international repository for all academic institutions. Each university has its database and access to it is not granted to any third-parties. The leading academic plagiarism checkers like Turnitin, Unicheck, have access to many private databases, improve their algorithms all the time and deploy new innovative products (authorship verification by Unicheck, or iThenticate by Turnitin). Still, the cheating methods are also ‘improved’ and changed every day. To combat academic dishonesty on time, the mixture of actions has to be applied where plagiarism software is only one of them.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .