Bloodstain Patern Analysis

By Kathy Reichs

Blood accounts for 8% of the weight of the human body. In the modern forensic lab, serologists type it and geneticists profile its DNA. Mystery authors and their readers are well aware of the value of body fluids in identifying victims and assailants. But the spatters and smears found at crime scenes have even broader applications in providing useful information. In addition to "who", bloodstains can determine the "how" and "where" of a violent attack.

For some time I have lectured at an annual homicide seminar hosted by the New York State Police. In the fall of 1998, while waiting my turn to speak, I listened to a presentation by Dr. Henry Lee, director of the Connecticut State Police Forensic Laboratory. Dr. Lee was using the Nicole Brown Simpson murder to illustrate his specialty, describing how bloodstains, either at a scene or on a suspect's clothing, can be used to a reconstruct an act of violence.

I was intrigued. What if the story told by blood disagreed with that given by a defendant or eyewitness? Having just begun Deadly Décisions, I decided to incorporate bloodstain pattern analysis into the plot. I contacted colleagues at the FBI Academy in Quantico, at the R.C.M.P. Forensic Identification Research Service in Ottawa, and at the Laboratoire des Sciences Judiciaires et de Médecine Légale in Montreal to learn all I could about spatter.

My apprenticeship was more interactive than I'd anticipated. There is a narrow side corridor at the LSJML, known to few, visited by fewer. The hallway leads to a small white room where the ceiling and walls are papered, and drops of blood cover every surface. Entering is like stepping into a slaughter house. The analysts dribble, stomp, and fling cow blood like post-modernist painters pelting a canvas.

Size and shape are telltale indicators. Individual spots range from 1/8 to as tiny as 1/1000 of an inch in diameter. The smaller the drop, the faster it traveled, so size gives clues to the manner of attack. Medium velocity spatter typifies an ax or hammer blow, while high velocity scatter suggests gunshot trauma. Shape reflects directionality. Droplets look like tadpoles or exclamation points, with their tails pointing toward the place of the injury.

Interest in bloodstains isn't new, but the methodologies of analysis have changed dramatically. Formerly, the point of impact was determined by attaching strings to a surface at the position of a stain, then stretching them back in the direction from which the blood was believed to have come. The process was repeated, stain after stain, string after string, until a giant web had been created. Home plate was the point at which the strings converged. Today computers combine the laws of projectile motion and the mathematics of three-dimensional geography with sophisticated graphics, and "virtual strings" determine the number of blows and the position of the victim at impact.

I find my work as a forensic anthropologist very satisfying. I enjoy being part of a team that searches out facts and fits them together, like pieces of a puzzle. Fragments of a shattered skull. Fingerprints. Paint chips. Bloody spatters on a wall. As death investigators, forensic specialists use these bits of information to establish truth and reconstruct past events in an objective way.

The crime lab and autopsy room are my turf, the world in which my stories take place. In Deadly Décisions Tempe Brennan is caught up in a murderous biker war. The body count is high, including that of a nine-year-old girl caught up as a bystander, and Tempe and her colleagues muster all their forensic skills to bring the carnage to an end. Bloodstain pattern analysis proves a useful tool in their arsenal of scientific detection weaponry.