Plagiarism is a scourge of the Internet age, so a free tool to check for student plagiarism sounds like a teacher’s dream come true. However, while the concept is exciting, the free version of PlagTracker is not yet reliable enough to be used with confidence.

PlagTracker works when the user pastes a school paper, or any other piece of writing up to 5000 words, into a text field at the PlagTracker.com site. Click Start Checking, and the service automatically compares the work with millions of web pages and scholarly articles. Once a report is generated, click View All Sources to see the links where the allegedly plagiarized material resides. Clicking the link alone may not work; I had to click the icon at the far right of the link to open it.

The Premium version of Plagtracker, which costs $15 a month, returns results faster, lets the user exclude direct sources of quoted material for more accurate results, and allows file uploads for *.doc and text files (instead of using cut and paste).

Can the free version of PlagTracker detect plagiarism? Yes. I wrote up a paragraph and incorporated, without attribution, an excerpt from a friend’s book. PlagTracker was able to identify the passage and page number via Google Books (though Google Books would not display the page itself). So that’s great.

Unfortunately, PlagTracker also finds plagiarism where it doesn’t exist. I uploaded a short (235-word) response paragraph that my son wrote for his 9^th grade English class, which I am reasonably sure was not plagiarized. PlagTracker determined that 48 percent of this paragraph was “non-unique.” In the free version, any material that appears in quotation marks without page or line citations is flagged on the grounds that it is not properly cited, and a link to the original work (if it is available online) will be provided. That makes a certain kind of sense, but PlagTracker doesn’t stop there.

For example, one of my son’s sentences went like this: "'People hate being wrong' is the second theme expressed in this story." PlagTracker flagged this line as problematic, and offered up five different sources supposedly casting aspersions on my son’s credibility. Four of these were sites where people pose questions for others to answer. The first source was Yahoo Answers, where last year someone posed this question: “I hate being outside and being around people. What’s wrong with me?” PlagTracker thought my son had plagiarized this site based on the presence of the "people," "hate," and "wrong," words you'll find extremely common on the Internet.

The second source was similar—an Askville question this time, wondering, “What’s wrong with homeschooling? (for people who hate the concept)." The third source led to a site called Answerbag ("Is it wrong to hate midgets?"), and the fourth to UK Yahoo Answers (“Why do people hate Know-It-Alls?”). The fifth source was the Wikipedia entry for Misanthropy. Why, I cannot say. PlagTracker isn’t telling. But none of these sources had anything to do with my son’s paragraph.

Another sentence my son wrote contained the words “New Haven.” Big mistake: This points to The Great Gatsby, three different versions of it, as well as a story called “Haven” at scribd.com. A teacher who is looking over the sources carelessly might assume, on the basis of the report, that my son had lifted passages from F. Scott Fitzgerald, but there’s no connection whatsoever. In this case, I would have been better off checking for plagiarism the old-fashioned way: Google.

I hate to imagine a teacher or TA pasting an essay into this “tracker” and then accepting at face value its conclusion that 30, 40, 50 percent or more of the document is “non-unique.” However, knowing that this is a relatively new project from a small team of Ukrainian computer whizzes, I plan to check in again in a few months to find out if it has improved with age.