Most of us first encounter the notion of plagiarism while we're in school. Countless schoolkids unwittingly become plagiarists when they write their first few research papers: they copy verbiage verbatim from an encyclopedia or Web article. Even elementary school teachers are quick to tell kids that's a no-no if they realize their students have done it. Often, though, the students are instructed to "put the material in their own words", and they dutifully do some rewording. The student (and, too often, his or her teacher) thinks this is fine, when in reality even a reworded passage still counts as plagiarism in academia if it's not cited properly.
Teachers (usually) crack down on plagiarism harder in high school, and most of us who had decent English instructors got citation and footnoting pounded into our heads. In my high school, unwitting plagiarism would get you marked down, but being caught willfully copying a paper would get you a zero for the whole project, potentially causing you to fail the entire class.
The stakes get higher in college; many professors have a zero-tolerance policy, and if they catch you plagiarizing a paper, they will flunk you without a second thought.
But you can always re-take a class. It's expensive, and being flunked is embarrassing, but you can chalk the whole thing up as a learning experience and move on.
Once you leave school and enter a profession in which your livelihood is tied to your publications, a plagiarism charge is a deadly serious prospect. If you are a reporter, novelist, scientist, or academic, being outed as a plagiarist can simultaneously wreck your professional reputation and put you at risk of an expensive lawsuit. In short, it can break you.
The trouble is, it's actually pretty easy for a working writer to unintentionally commit plagiarism. I've known of two good authors who committed plagiarism. I've changed their names, even though one involved a public court case:
Case #1: John Doe and the Plagiarized Novel
John Doe is an up-and-coming writer, not a big name, but he's made some story sales and sold a first novel. His younger brother Sam is really excited about John's publishing success, and Sam says he had a great idea for a book. John agrees to write his next novel based on his brother's ideas. Trouble is, Sam had gotten all his ideas from an older, not-well-known horror novel written by a very prolific well-known writer we'll call Mr. Big. John doesn't know this.
So, Sam outlines the plot and characters -- taken almost verbatim from Mr. Big's book -- and gives his notes to John, not realizing that what he's doing is wrong and dangerous. John thinks his brother's ideas are awesome, and starts writing the novel. The novel is in John's style and his own words, but the characters and plot are almost identical to the other book. Sections of dialog, courtesy of Sam, are identical. When it's finished, he gives it to his agent (who hasn't read Mr. Big's book) who thinks it's great. The agent sells it to a publisher who also hasn't read Mr. Big's book.
When the novel comes out the next year, other people read it who have read Mr. Big's book. Someone sends Mr. Big a copy of the novel -- and he's furious he's been ripped off by some punk upstart.
John, still not realizing what his brother's done, insists he's innocent. Mr. Big takes the case to court. John is found guilty of plagiarism and is ordered to pay Mr. Big a fairly large settlement. John suffers a great deal of public embarassment, loss of professional reputation just as he is actually starting to have one, and has to pay Mr. Big the equivalent of a small house mortgage for many years. He suffers tremendously because his brother was copyright-stupid and John didn't think to ask where his great ideas were coming from (and also because neither he, his agent, nor the publisher were well-read enough to catch the novel's problems, but that's another issue).
Case #2: Sally Smith and the Plagiarized Story
Sally is a published story author and academic. Like many writers, she keeps a notebook of ideas she jots things in as they come to her. She also jots down particularly cool, quotable passages she finds in the many books she reads. She is always careful to note where she found the passages -- except once, she slipped up. She wrote down a paragraph from another writer's short story, but got distracted before she cited it.
Ten years later, Sally's published a metric ton of her own fiction in books and story collections. She's asked to write a story for an upcoming anthology, and so she starts thumbing through her old notebook for an idea. She spies a nifty paragraph -- the one from the other writer's story -- and inspiration strikes.
She sits down and writes a story that flows effortlessly from her fingers; it feels familiar to her, but by now she's written hundreds of stories and she dismisses the feeling. The finished story is very similar to the other writer's story. Not identical, not even similar enough for many people to call foul over ... but she's got that one paragraph in there, and it's word-for-word the same.
Her story's published in an anthology, and then she sells it as a reprint to another anthology. Nobody notices anything's amiss. Then, one day, one of her readers sends her an email: "I really enjoyed your new story, but wasn't it a lot like Richard Roe's story in New York Tales?"
Her memory pings. She digs out her old issues of New York Tales and finds Roe's tale. Sick horror overwhelms her as she reads his story and realizes why writing her recent story felt so familiar to her -- she read it ten years before, and used it in her notebook!
She realizes that something like this could ruin her reputation, and on top of that she feels horrible for inadvertently ripping off another writer. So, she sends Roe an apologetic letter explaining what happened, and asks Roe what he wants her to do.
Roe's met Sally before, enjoys her work, and respects her as a writer. He accepts her explanation, and says that he'll be satisfied if Sally sends him the money she got for the story with the understanding she will never try to sell it again. And finally, he has her copyright the story under both their names. He doesn't take her to court, and the matter remains private among him, her, and their agents. Sally's cost is a few hundred dollars and some personal embarrassment. Her reputation remains intact, and everybody goes on with their lives and the incident is pretty much forgotten.
As you can see, there's always a price to pay for committing plagiarism, even unintentionally. But by coming clean and being upfront and contrite about your mistakes, you can potentially avoid the worst. If you gamble that nobody will notice, you run the risk of having the charge taken to you by an angry author who won't be much inclined to believe your explanations (especially if you cop an attitude with him or her). If you try to cover up, you make yourself look guilty, and you're not likely to do well in court.
If somebody accuses you of plagiarism and you genuinely think the charges are unfounded, by all means, fight them -- but first, make sure they are unfounded. Don't cave to a crackpot who thinks that just because you also named your main character William Ballinger that you owe him a chunk of money. But if you know you screwed up, just 'fess up and try to do damage control.