Q: The Killer of Little Shepherds: A True Crime Story and the Birth of Forensic Science is the true story account of a serial killer, Joseph Vacher, loose in the French countryside during the 19th century just as the field of forensic science was growing; it would lead to his apprehension. How did you come across this moment in history and what drew you to investigating it in this book?

A: I’ve always been interested in stories in which science plays a role in human drama, especially mysteries. I started on several projects, one of which involved following a murder trial that involved DNA, but none of those ideas panned out. Then one day, while poring through some medical journals, I came upon a thesis about the case of the serial killer and the scientist—Joseph Vacher and Dr. Alexandre Lacassagne. I became fascinated with the pioneers of forensic science, or CSI as people call it today. I also was drawn to the period. The turn-of-the-century was a lot like our own time: it was a period of tremendous scientific advancement, yet a time of great anxiety as well. There was a troubling gap between the haves and have-nots. A global terrorist movement, anarchism was rising. It was also an amazing turning point in human history, when the questions of good and evil moved from the realm of the clergy to that of the scientists.

What captivated me most, however, were the characters. Vacher was not simply evil. He was a man consumed by pain and self-pity, capable of soaring passions, but also unspeakable crimes. On the other hand, Dr. Lacassagne personified all that was admirable about his era—educated, humane, a renaissance man, not only in the field of criminal analysis, but in other areas of social progress, including public health and prison reform. He genuinely believed that science could solve the problems of society. He was remarkably unprejudiced for his times, and in many ways was ahead of his era. I wish I could have met him.

Q: Joseph Vacher has to be one of the worst serial killers in history—compared to the infamous Jack the Ripper, who killed five prostitutes in London, Vacher attacked his victims across all of France, focused particularly on the young and vulnerable, and killed between 11 and 25 people (the total remains unclear), far surpassing Jack on every point. Why do you think Vacher remains unknown? Was he infamous in his own time?

A: Vacher was quite well-known in his time: his capture and trial made international news. In rural areas he became synonymous with the bogeyman. After his execution the story faded away, except for some newspaper coverage of the autopsy of his brain and the search for the origins of his murderous impulses.

I think the reason that he disappeared into obscurity, while the name of Jack the Ripper continues to live, is that Jack was never caught. He taunted the authorities in the course of his killing spree, but no closure was ever brought to his story. To this day, every few years, someone comes up with a theory about who Jack the Ripper may have been. The case of Vacher was open and shut—there was never any question of who committed the murders—although no one has ever been able to understand why.

Q: Your book is full of precise details— evidence from crime scenes more than 100 years old, meticulous portraits of those living through the brutality of Vacher’s killing spree and insights into his psyche via diary entries and medical records. You also portray those chasing Vacher, most notably Alexandre Lacassagne, one of the founding experts in the field of forensics. How did you go about doing the vast research for this book?

A: One of the problems in writing historical nonfiction is that no one is alive to interview, so you must recreate the story from whatever historical records you can find. This recreation must be scrupulously accurate. Every fact and quote in the book has to come from a verified source. So I had to do a lot of old-fashioned digging.

In order to recreate the crime spree, I traveled throughout France, digging up legal documents, newspaper accounts and scientific material. It was a scavenger hunt, and I didn’t know if the hunt would succeed. Fortunately, I got lucky. In the provincial city where the trial took place I found several crates of documents, including court records, eyewitness testimony, a collection of letters from the killer and transcripts of the trial. I visited an insane asylum where the killer had been committed and saw the original psychiatric report. I gained access to the prisons where Vacher was held. I found details about the crimes in the original autopsy reports.

In order to get a sense of time and place I traveled to the villages where the killings occurred. I interviewed elderly farmers about local history, lore and life at the time of the story. One of them told me that his grandmother narrowly escaped being murdered by Vacher. Another told me that his great-uncle was one of the villagers who helped capture the killer. Other old farmers took me to the sites of the murders, so I could get a visceral sense of the times and place. This was invaluable information that I never could have obtained from documents.

On the scientist’s side of things, I spent many days in the archives that Dr. Lacassagne left behind at the University of Lyon. His great-great-grandchildren also graciously shared many of his materials. He had a summer cottage a couple of hours outside Lyon, which is preserved to this day with many of his artifacts—visiting that house was like stepping into a time capsule.

To better understand forensic procedures, I sat in on a couple of criminal autopsies at the institute of Legal Medicine in Lyon. That was quite an experience—one that I don’t wish to repeat.

Of course none of this would have been possible without many people in France who helped. One was a remarkable a man named Rémi Cuisiner, a retired tile-layer and self-educated historian, who lives outside Lyon. He thoroughly knows the back country of France, and took me on road trips to make contact with villagers. Many of these people were elderly farmers who had never met an American before, and they would have been suspicious without my friend’s introductions. He also translated their regional dialect into standard French, so I could understand them.

Q: Was it difficult to deal with some of the more gruesome facts and materials that you discovered?

A: Yes! Frankly, the material was terribly gruesome and more than once intruded into my dreams. In order to re-create the murders I worked backwards from the original autopsy reports, which spared no details in describing the victims. The reports were accompanied by line drawings, which, even though simple, were very disturbing. As part of my research, I sat in on a couple of criminal autopsies at the Institute of Legal Medicine at the Lyon–sights and smells that are not easily forgotten. But they were invaluable to the story. There’s a scene in chapter 2, for example, that’s taken directly from my observations of a putrefying body.

Q: Alexandre Lacassagne, a pioneer of forensics, emerges as Vacher’s nemesis in the book, tracking him across the expanse of the French countryside and many years’ time. Are the techniques that Lacassagne developed and that we see him use in The Killer of Little Shepherds still relevant today or has the field of forensics completely changed?

A: Many of the techniques that Lacassagne and his colleagues developed became the foundations of CSI work today. He personally figured out rifle bore analysis, in which the markings on a bullet can be matched with those of a particular gun. He also systematized autopsies in a way that made the evidence-gathering procedures more reliable. He and his colleagues figured out how to recreate crimes by analyzing blood-spatter patterns and the positions of bodies, and the distribution of blood within the organs of the deceased. They figured out the science of biometrics, in which characteristics of the body (including patterns of the iris) can be used for positive ID.

Of course these techniques have been modernized over the years. But the basic notion—and the understanding that evidence can tell a more accurate story than testimony—were developed by the pioneers of CSI in the late nineteenth century.

Q: America is fascinated with forensic science—millions eager for the hit TV show CSI and its two spin-offs, the video game and comic book, not to mention the permeation of forensics into thrillers, mysteries and dramas of all kinds. To what do you attribute this fervor? Were you yourself a fan before you came to this story?

A: I was not a major CSI fan before I came to the story, although the book has made me interested in the show. Now I find myself tuning in to watch their techniques and see which have their origins in the days of Dr. Lacassagne. Of course the original CSI stories took place more than 100 years ago, in the fictional character of Sherlock Holmes. I’ve been a Sherlock Holmes fan since childhood. As I discuss in the book, Dr. Lacassagne himself became a fan when the stories first appeared during his career. Lacassagne had one of his graduate students write a thesis on whether the science of Sherlock Holmes was consistent with the real forensics of the 1890s. Holmes was the prototype for the cool, scientific personality who used his intellect to work against evil. So was Dr. Abraham Van Helsing, the scientist who defeated Dracula, another fictional villain of the time.

Sherlock Holmes and the scientists of CSI have much in common that appeals to us. We live in perilous times, with lurking threats from terrorism to global warming. Life seems so dangerous and chaotic—we want order and intelligence to triumph. And here we have heroes—whether Sherlock Holmes or Horatio Caine—who effectively use science to triumph over crime. There’s something reassuring about their cool, scientific professionalism; a sense that competent people are in control. Also, let’s not forget the stunning graphics, visually exciting sets, and beautifully-dressed actors.

Q: In addition to the hunt for Vacher, The Killer of Little Shepherds focuses on the attempt of the society and the judicial system at that time to answer – what is justice for this man, for this case? Is he sane or insane? What punishment is appropriate? What did you learn looking at the way those questions, questions still asked daily, were investigated and answered at that time?

A: Serial killers almost always have been exempt from the classification “insane,” because the planning, committing, and covering-up of their crimes takes so much forethought and care. We put them away for life, or in some states, execute them.

Our assumptions about serial killers are now being challenged. The latest neurological research is showing that the brains of some psychotic killers actually may be damaged—that the circuitry that normally controls the brain’s primitive impulses does not properly work. In other words, certain criminals, while knowing their impulses are wrong, truly lack the ability to resist them. The idea, one almost too frightening to contemplate, is that some small percentage of serial killers may be born with that tendency.

That same question was investigated and debated by the characters in my book. Rather than using modern MRI machines, they conducted tests on prisoners and dissected their brains after execution. Like their modern counterparts, Dr. Lacassagne and his colleagues struggled to understand why certain people committed such heinous acts. It was all part of an ongoing search to understand the darkest impulses of the human mind and soul.

I think this story goes to the heart of some of the most troubling questions facing humanity—namely, why do people commit horrible crimes?

Over the years we’ve made tremendous progress in analyzing what happens at a crime scene, but we have a long way to go in understanding why. Indeed, ever since Dr. Lacassagne’s day, we’ve hoped that with good enough science we’ll someday be able to identify the forces that result in horrific crimes—and maybe learn to prevent them. But we still can’t pinpoint the sources of evil, despite our incredibly sophisticated science. As a thinking person I can’t accept the simple explanation of good vs. evil, but I wonder if that basic question will ever be resolved. What turns people bad? Why do some people kill—and kill horribly? The questions that haunted Alexandre Lacassagne haunt us to this day. His quest is our quest. Illuminating that search—a key mission, I believe, in the progress of humanity—is fundamentally why I wrote The Killer of Little Shepherds.