Welcome to the next installment of my irregular series of tips for writers. The material that follows is adapted from How To Write Killer Historical Mysteries: The Art and Adventure of Sleuthing Through the Past (Perseverance Press, 2008) by Kathy Lynn Emerson (aka Kaitlyn Dunnett).

How do you evaluate a secondary source? First check the publication date. Then take a look at the bibliography and footnotes if any. Be wary if no primary sources (documents, letters, newspapers, and so on) are listed. If there is no bibliography at all, be very suspicious of the contents. Also see what you can learn about the author’s expertise in the field. It isn’t necessary to have a Ph.D. to be a good researcher, but there should be something motivating the writer to delve into the past. An enthusiastic amateur scholar obsessed with tracking down an ancestor, for example, may prove to be a wonderful source of accurate information. An academic in a rush to publish something in order to keep his job may be somewhat careless about checking facts.

Nonfiction or not, biographies and histories are often written with an agenda in mind. Academics are not unbiased. History is constantly being rewritten. The author’s pet theory or bias may color which historical facts are emphasized in the text. Take any controversial moment in history and you will find radically opposed arguments in print about what really happened and why. In reaction to years of neglect by scholars of the distaff side of history, the 1980s saw a proliferation of books with a radical feminist, revisionist slant. Some aren’t any more accurate than the books that ignored women’s roles completely, but they did increase the amount of information available on domestic life.

Many secondary sources simply rehash the contents of older works.That means they may be repeating misinformation. If the first person to transcribe or translate a document got it wrong, that mistake may be repeated in multiple sources over the years before another scholar goes back to the original and catches it. I was guilty of this myself in one of my nonfiction titles, Wives and Daughters: The Women of Sixteenth-Century England, provides a good example of what to be wary of in a reference book.

This book was written because I had accumulated a great deal of research in order to write historical novels. None of these early fiction attempts sold but I hate to waste anything. So, in 1979, I started trying to sell a sort of Who’s Who of sixteenth-century women. The proposal was rejected by just about every publisher (“too scholarly” for a general audience, “not scholarly enough” for university presses) but finally found a home with a small independent scholarly press. This was my first book sale. I knew nothing about contracts and did not have an agent and ended up signing away far more than I should have. Why do I mention this? Because the book was in print for twenty-five years and is still available as a used book.

The original Wives and Daughters was a handy reference book for its time, but its time was 1984, before the Internet made research so much easier. The material this book contains is almost thirty years out of date. Does this matter? In some cases, no. But this is a collection of mini-biographies of 570 sixteenth-century Englishwomen. In at least a few cases, previously undiscovered documents have come to light in the interim. Add to this the fact that a great deal of information I was unaware of when I was writing the entries in 1980 (yes, it took four years for the manuscript to reach book form) can now be found online, and my book as a whole must be considered unreliable.

An aside here: when I finally got my rights back, I created an updated, corrected, expanded (currently over 1700 entries) and free version online. I continue to expand it as I find new and interesting people to add or stumble on interesting tidbits I haven’t seen before about women already included. To look at A Who’s Who of Tudor Women (after you’ve finished reading this post, of course), start at http://www.KateEmersonHistoricals.com/TudorWomenIndex.htm and explore from there.

Books that do not contain footnotes are usually suspect as reliable reference books. In this one area, I’ll claim an exception for my Who’s Who, simply because most of the entries in both versions have been compiled from a sentence here, a footnote there in histories and biographies about sixteenth-century England. Footnotes would more than double the size of the work and not be particularly useful.

The bibliography in both versions is one of the “select” variety. In other words, it includes only the books that were most useful. Any reliable nonfiction book should have a bibliography. Check the dates of the books listed in it and, as with the copyright date of the book itself, you’ll have a guide to how up-to-date the information is.In the case of Wives and Daughers, the bibliography is only seven pages long and contains no book published later than 1981 (and only one that late). One of the entries may be a good starting point for a character in your historical mystery, but you should seek out more recent works for further information. For example, a 2001 biography of John Dee (Benjamin Woolley’s The Queen’s Conjurer) contains much more information about Jane Fromond, Dee’s wife, than I was able to find in 1980. It’s 2013 now. In twelve years, even more has come to light. Jane’s online entry in A Who’s Who of Tudor Women has been revised accordingly.

Common sense is the best guide to knowing when it is safe to use someone else’s research. If you question a “fact,” find more than one source for it. The more you read about your chosen historical period, the better you will become at spotting someone else’s sloppy research. A red flag will go up when you find an error. If you do find a glaring mistake then, sadly, the entire book should be considered suspect.

One reputable scholar, in his book’s chapter on food, makes the statement that Henry VIII banned all stews. Thus, this writer concludes, it was forbidden to eat this particular dish during the sixteenth century. In fact, the “stews” legislated against were whorehouses. That isn’t a mistake you want to repeat in your historical mystery . . . unless you’re going for a laugh.

And yet, if you are writing fiction, you are trolling for details that will make that fiction come alive. You are not writing a dissertation. Sometimes it is possible to find inspiration in a source that isn’t all that accurate.

I researched brothels for Face Down Among the Winchester Geese, in which several scenes are set in the stews of Southwark. One of the books I consulted deals exclusively with these brothels, but it contains several mistakes in historical fact. Calling Mary Boleyn (Anne’s sister) the long-time mistress of Henry VII when she was really the short-term mistress of Henry VIII was the red flag in this case. That and other errors make all the material in the book suspect. But it contains wonderful, evocative details, things I wanted to be true. The author maintains, for instance, that pictures of individual prostitutes were hung on the walls of some brothels in order to allow customers to make their selection. As I plotted my book, I wondered whether or not I could trust this “fact.” The sixteenth century was a time when only the wealthy could afford to commission portraits. But was there some way I could use this detail anyway? If I did, for myself and for my readers, I knew I’d have to have a reason why it could be true. I decided that an impoverished artist might have traded his work for favors. Did any real brothel in Elizabethan times have such portraits? I don’t know. But for the reason I gave my readers, mine could.