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Detecting plagiarism : a self-help guide

when to suspect, how to detect, how to stop it happening in the first place!

John Royce, Library Director, Robert College of Istanbul
See also the various presentations on Plagiarism at <>.
A constantly updated bibliography is available at <>.

Alarm bells

It is commonly thought that the most reliable sign of plagiarism is when a student suddenly produces work of far better standard than previously submitted.  This may well be true. However, while sudden rise in quality might well indicate plagiarism, lack of quality does not guarantee that the work is the student’s own. Many of the essays available from internet cheat sites are of mediocre quality, much of the material on the internet is of dubious and mediocre worth.
Some obvious signs of plagiarism can be found on Plagiarizeddotcom’s page of Dead Giveaways at
You might also be suspicious when:
Several different styles of citation are used. This could indicate lifting from several documents, each using a different style of citation.
References to pages are suspicious - especially if you know the work cited. Note too that few school level text or information books run to 700 pages...
The level of works cited is way beyond the capability of the student.


If you do not know the authors, check the references, find the books, check the web sites... 
Some printed works may be so advanced your school library may not have a copy. 
You can sometimes check how advanced a book is by going to an online bookstore! 
Citations refer to items not included in the bibliography. This might indicate lifted work, the passage/s simply copied and pasted without thought.
There are references to tables or illustrations not included in the paper. This too might indicate lifted work, the passage/s simply copied and pasted without thought. 
Many full-text databases include text, including references, but do not carry the graphics mentioned in the text!
There is a failure to cite good evidence. This could mean that the evidence is invented; evidence such as quotations, statistics and similar must show sources.
There is a mix of spelling, eg UK and US spelling, or foreign names are spelt in two or more ways. Again this might indicate lifting from several documents, especially when the differences are not accidental (for example:  occasional writing of Philip and Phillip might be accidental; cavalier interuse of Don Juan and Don John or of Philip and Phillippe are likely to show two or more sources have been used without proof reading).
There are non-sequitors, bad leads from one paragraph to another, the joins don’t sound right. Could indicate several different documents have been used.
The level of language or the tone changes from paragraph to paragraph. Could indicate several different documents used. 
Could indicate a mix of lifted passages and student's own work.
There are no citations or no bibliography at all.


Even without suspicion of plagiarism, this could be enough to downgrade the work.  Where is the evidence? 
But be sure: were your instructions clear, were students aware of the need to produce a bibliography? Have they been instructed in when and how to cite?
When there aren't any citations or references, downgrade the work. 
When there are references and citations, follow them up.

All the above are indications, not proof, of plagiarism.
You still have to prove your case
by finding the original source/s the student has used.

Tricky kids
Students use a variety of tricks to hide their plagiarism. Tracking and tracing requires a lot of work, and it pays to be aware of some of the tricks used.

Cheating students often

Copy a large section but reference or quote just a small portion of the lifted passage. Check the citation; look before and after the section in quotation marks.
Build a pastiche from several different sources. Thus the need to check for keywords in close proximity.
Make up quotations and citations. Check the citation. If it's a real source, check that this is what is said. If you can't find the source, ask for photocopy or printout.
Misquote or misinterpret what was actually said in the original, the better to suit their own arguments. It could be a judgement call: deliberate cheating or real misunderstanding? Your knowledge of the student and/ or number of times it occurs could be factors.
Make up false citations and references
  • Using an author/ periodical which is available in the library, rather than the one cited in the original;
  • Inventing an author or source;
  • Using a real web site (but not the one from which the information is lifted);
  • Referencing the home page of a web site but not the actual web page used.
  • The fact that an author exists, that s/he really did write a magazine article or a book with the title as shown, the fact that it is available in the library, perhaps even a book that the instructor has read, all these serve simply to mislead. When you are suspicious, you must check those citations and references. 
    Similarly be wary of web site URLs and check them. If you cannot find the page, demand a printout. (Ideally students will be warned in advance that printouts may be demanded.) But the internet is unstable, pages do disappear; the fact that you cannot find a page is not necessarily proof of cheating, and it is also possible for page contents to change between student discovery and your checking. It is suspicious but not necessarily proof. Printouts can help you decide.

    When you suspect plagiarism:
    Try these techniques and strategies, in the order shown and as appropriate:
    Number One Rule:

    Check any citations given, follow up any works listed in the bibliography.


    • Ask to see copies (or photocopies) of books and journals used, printouts from web sites etc.
    • Does the library have the books/ journals cited?
    • Check citations, are they genuine? Are they accurate?
    Cheats sometimes make up quotations and paraphrasing (though sometimes it is a case of misunderstanding what they are paraphrasing);
    sometimes they use a genuine quotation but change the attributed source, perhaps to reflect what is actually available in the local library;
    sometimes they make up the URLs and web sites they claim to have used;
    sometimes they quote and cite correctly a sentence or two, but in fact they have lifted a page or two or more.

    All this should become clear if you go to the sources used (or claimed).

    Think about what you already know.  If it sounds familiar, it could be you already know the source: an author’s style, an article read recently, esoteric references: anything that rings bells is worth checking on.
    Think about any fact, statistic, statement used which should have an attribution, but does not. Where did they get this information? How do they know? What PROOF is there?

    These are amongst the basic reasons for academic citation.   Be suspicious when facts are given without citation - and go looking for the source of these facts!

    Make an internet search for the title. Use several search engines and a meta search engine or two. 
    Don’t forget to put the title in "inverted commas" to make a phrase search.
    Search the internet for any pictures, diagrams, or other illustrative material. When you find a picture that matches, start checking the text. Students who download pictures often download and copy the words too!


    Make an internet search for unique keywords.



    • Use several search engines and a meta search engine or two
    • If two or more words, put them in inverted commas
    • Use several combinations of unique keywords, first scattered through the document, then keywords in close proximity.
    This scores when a large part of the paper has been copied from a single source.
    Make an internet search for phrase or keywords in close proximity.




    • Use several search engines and a meta search engine or two.
    • Use combinations of phrases and keywords in close proximity; repeat from different places through the document.
    • Put any search phrase inside "inverted commas".
    • If a particular word looks or feels awkward, just try using a more natural synonym.
    The paper might be part original, part lifted; it may be totally lifted but from a variety of sources. Checking words in close proximity increases the chances of finding the words together in the same document.  Check from several places through the essay to increase the chances of finding any (and possibly every) different document used.
    Search the invisible web.
    Search engines index only a small proportion of the internet; some restrict themselves to the World Wide Web. 
    Much of the information in the invisible web is valuable, pertinent, easily accessed and free. Get to know how to search the invisible web! 
    Check your school / public library. 


    It is just as easy to copy and paste from a cd-rom as it is to copy from the internet - and of course, if it's not on the internet, no amount of searching will find it there

    Online databases are rich sources of information which, because they are usually on subscription basis, are NOT searched/ indexed by search engines. You must go where the kids go, must use the resources the kids use!

    Don't forget the books and other print (and non-print) resources available to students in the library.

    Use your networks.


    Ask colleagues at your school. 
    Ask colleagues in other schools. 
    Use listservs, newsgroups and so on.
    Check the anti-plagiarism sites, use a free or fee-paying plagiarism detection service.


    Amongst the many services are Findsame; TurnItIn;; EVE2; Internet Essay Explorer; Glatt Plagiarism Services;; Digital Essays; IntegriGard; Some are free, some cost, some have trial offers. None of these is perfect and all results require further checking

    Be wary: a clean bill of health does not necessarily mean the piece is genuine and plagiarism free. On the other hand, a possible match may not necessarily prove that the piece has been plagiarised; none of these services is perfect and ALL results require further checking.Use the results as indicators only. You still need to follow them up.
    The great value of TurnItIn is its growing database of work submitted on suspicion. The hope is that essays NOT found on the internet will be submitted, and those copying from each other rather than using online services will in time be caught.

    Check the cheat sites.


    It could be worth looking for essay titles and / or subjects on the cheat sites and paper mills; those which do not publish their essays online usually include an abstract, and indicate number of words or pages, number of citations, number of items in the bibliography. The number of pages is no guide at all (student may use a different font and thus have more or fewer pages); the number of citations and items used can be an indicator.
    Check Google Answers.


    Google Researchers normally try to avoid answering directly any question which looks as if it is a school assignment, preferring to explain what is needed, and to direct the inquirer to some resources which could be helpful. Many assignment questions may well get through. It could be worth going to Google Answers and using the search tool on the home page. 
    Google Answers is part of the invisible web! 
    Google itself does not search and index Google Answers!! 

    Check Google Print, Google Books (which includes magazines), Google News Archive, Google Scholar...

    It could be an outside chance - but if you are desperate it's worth trying.
    Since late 2003, it has been possible to search the content of many of the books stocked by
    Simply enter some suspicious keywords, and check out what comes up. 

    Google presents ever more options and possibilities.  Not all of these are direcly searchable, but they could suggest avenues to explore.

    Number Two Rule:

    At any time during the above, ask your librarian.

    The school librarian may have an inside edge, eg knowledge of resources in library which could have been used, knowledge of places to search online and offline, may have more advanced techniques and strategies and tricks up her or his sleeve. 
    S/he will also have a wider knowledge of invisible web resources, as well as awareness of what is available in hard copy rather than online!

    Which search engines?

    Current favorites include Google, Northern Light, and AllTheWeb, favorite metasearch engines include Ixquick  and Vivisimo.  Also use Yahoo!: it may not be the best search facility, but it is favored by many students and could lead you straight to their source. provides quick access to a number of sources and search tools.

    Use several search engines; they search different areas of the internet and/ or the web, and they yield different results in different ways. There may be little overlap between the hits of one search engines and the hits of another, so the more search engines you use the better your chances of detecting (internet) plagiarism.

    Open links in new windows.

    Use <Ctrl+F> to find keywords on a page, in a document.

    Develop a sense of which hits or leads to follow, which to ignore.

    When evidence is difficult to find  
    You don’t need to prove the whole thing has been lifted, once you have made a few finds or found that a significant part of the essay has been lifted, you may be able to stop searching if it is proving time-consuming.  Of course, the more you can prove has been lifted, the more serious the offence. 

    You might just keep a copy for future reference, or to try as your search skills develop.  You might even find the same essay submitted next year... 

    You're not going to catch them all: without giving ideas to students who don't already have those ideas, there are just too many sources of information available to make plagiarism detection easy and foolproof. Vigilance and awareness is necessary - and better still, an ambience where students find cheating counter-productive, demeaning and self-defeating. 

    Above all, don't forget: if you can't find proof of plagiarism,
    it could mean that the student really is innocent!

    Prevention is better than cure
    A constantly updated bibliography is also available at <>.

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    John Royce, BA, MLib, MCLIP
    Library Director, Robert College
    Arnavutköy, TR-34345 Istanbul, Turkey.

    The URL of this page is
    It was last revised on 23 December 2008.