DNA AND THE SAVVY WRITER by Maria Hudgins

Police have identified the person whose sweat was left on a button on the knife sheath found at the scene of the bloody murder of four college students in Idaho. Think about that. One touch and he has left his calling card.

Reading this takes me back to the most exciting time of my young life. I was a graduate student at the University of Tennessee, taking a course on current work in biochemistry. This was about 1964 or 1965. It was a seminar course where we would read and discuss the latest publications about a new thing called DNA. At this time Watson and Crick had received the Nobel Prize. We knew that this was the molecule found in every living cell and that it contained the instructions for making a new mouse, a new rose, or a new you. But we didn’t know how it did it.

I remember that some of our seminar discussions ranged from the sublime to the ridiculous. How could a chemical spell out something as wonderful as . . . us? Looking back on it now, it seems obvious. Why couldn’t we see it then? DNA contained four smaller units called, A, T, G, and C. Never mind what these letters stand for. These four units were like a tiny alphabet. It took a few more years for scientists to learn how to read the words. A few. Once the basic idea was accepted, the rest followed like water through a broken dam. It was mind-blowing.

By 1984 DNA could be used to identify individual people. By 1990, gene therapy could be used to treat immune deficiency diseases. 

In 1995, jurors in the O.J. Simpson murder trial ignored definitive DNA evidence because, they told reporters, they “didn’t understand it.”

In 1997 Dolly the sheep was cloned from a cell taken from an adult ewe. By 2003, the Human Genome Project containing the entire map for human chromosomes was complete.

As writers and readers of mystery fiction, we should know this history. A story set in World War 2 must not have a detective sending a blood sample off to the lab “for analysis”. Beyond the basic blood types, A, B, O, and AB, there would be nothing the lab could tell them. A story set in 2001 should not have a detective sending off a hair to the local lab and getting back anything in a few days. Today, the FBI keeps a database of DNA profiles called CODIS, and your perp may be in it if he or she has had unpleasant business with the feds.The amount of information, the cost of tests, and their reliability have improved dramatically and at lightning speed, but they are not yet perfect.

As the science has improved, we have found deep flaws in some accepted techniques like bitemark ID, hair analysis and blood spatter analysis. The more sophisticated DNA science becomes, the easier it becomes to make mistakes. We are now working with teeny-tiny samples.

The mystery writer must keep up with the science because the reader may know more than you do. Then again, he may know much less and you don’t want to bore him with dry lectures. Writers, you can avoid the whole problem by setting your story in the past. But then you must know your history. There are no easy options. No wrist watches on George Washington’s men. No cavemen fighting dinosaurs, and no way to identify a person from a sample of his blood.