Today’s Words of Wisdom takes a fact-based, real world turn and looks at the science of forensics. Lisa Black, Sue Coletta and Garry Rodgers all provide facts and insights which can help your fiction writing, be it mystery, suspense, thriller. Even more than usual, it’s well worth reading the original posts in full.
I do not make a habit of taking my plots from real-live cases—it always sounded like a good way to get sued to me—but the germ of an idea for Evidence of Murder did come from a case I worked with the coroner’s office in Cleveland, Ohio. A woman who worked as an escort—quite legitimately, through an agency that could be looked up in the phone book—disappeared from the face of the earth after one final date. She had a steady live-in boyfriend and an eight year old daughter. The story stuck in my mind for two reasons.
One, escorting (if that’s what it’s called) seemed like an odd way to make a living—at least to me, having been married long enough that spending every night with a different man sounds like an agonizing amount of work. Certain readers may be disappointed, but very little of the book refers to the victim’s job. For the most part it is mentioned only to point out that every person she encountered wrote her off as a brainless bimbo, including—at first—my main character, Theresa MacLean.
Two, it was one of those cases where the cops were positive they knew whodunit, but could not prove it. One huge disservice that the television shows do to the field of forensics is to insist that you can always find more evidence if you just look harder. Yeah, right. That’s like saying doctors could cure cancer if they really tried and obese people would be thin if they’d only eat less. Sometimes a clue (or a cure, or a solution) simply isn’t there. Sometimes cool things are there but may not be clues. I have a mental list of my real-life cool clues that never went anywhere. In one high-profile case where a mother of three was abducted from the parking lot of the local mall and later found assaulted and shot to death in her own van, I kept finding rabbit hairs dyed a brilliant cherry red. The family had only just bought the van and gave me every set of hairs, every coat, every piece of clothing they thought might have been in it. I asked the detectives to keep an eye out for some fun fur trim or a lucky rabbit’s foot (though those had fallen out of style by 1996). It never turned up. By the time we caught the killers, a year had passed. No red rabbit fur. Another time I was examining the raincoat of a murdered prostitute under ultraviolet light, looking for semen or fluorescing fibers. At one spot on this plastic raincoat a pattern leapt up—a crystal-clear design of stylized daisies, something that would have been popular during my childhood in the late 60’s or early 70’s. Obviously the raincoat had been up against something with fluorescent properties and, for some obscure chemical reasons I couldn’t begin to guess, transferred to the vinyl. In regular light, the pattern became invisible. I described it to the detectives but again, no bells rung. In forensics, contrary to what you see on TV, you have to make your peace with not knowing everything.
Sometimes clues are there but can’t tell you enough. Finding the hair of the victim in, say, the trunk of the suspect’s car might be very incriminating—if he says he never met the woman, it might be enough to convict him. If he happens to live with the woman, it means exactly nothing, since her hair is likely to be all over the apartment and easily transferred to items he might put in the trunk. Or she might have dropped it there while leaning over to take out the groceries. Or it might have fallen out when he transported her body to the dump site. There’s no way to tell. So I wanted to explore what happens when every physical clue Theresa finds simply leads her to a brick wall instead of some helpful revelation.
Lisa Black—September 9, 2009
Teeth Show Time of Death
When no clues exist to identify a corpse, investigators have a serious problem. The determination of age and sex of the body can be crucial to limit the search for individuals that could possibly match missing persons records. Today, gender can be determined through DNA, as well as the skeleton itself, but believe it or not, it’s not as accurate as testing done on teeth. Age estimation in children and adolescents often depends on radiological examination of skeletal and dental development. In adults, however, age estimation is much less accurate.
Enter: aspartic acid racemization and radiocarbon dating.
At the sprawling 26-acre Freeman Ranch in Texas, over 50 human corpses reside at the body farm. Many of which are checked via drone. Scientists examined 44 teeth from 41 individuals using aspartic acid racemization analysis of tooth crown dentin and radiocarbon dating of enamel. Of those, ten were split and subjected to both radiocarbon and racemization analysis. Combined analysis showed that the two methods combined worked better than relying on one or the other.
Radiocarbon Dating, a forensic tool also done on eyes, is an accurate way to determine environment, date of birth, age of deceased, nutrition, diet, and even date of death. I’ve written about Radiocarbon Dating before (see link above). Briefly, similar to counting rings on a tree to determine its age, same applies to the eyes and teeth. Only with teeth researchers aren’t looking for crystallins.
Twice a year each permanent tooth is anchored to the gums by tiny, distinct fibers. A bright line is laid in the spring or summer, depending on where you live, and a dark line in the fall or winter. The number of bands, as well as the color and width of the outermost ring, help scientists estimate the deceased’s age at death and also narrows the TOD (time of death) window.
Plants and Trees Love Dead Bodies
Human remains act like any other type of fertilizer, producing nitrogen that leeches into the soil. and provides nutrients to plant-life. Trees and plants thrive on this added nutrient, growing taller, fuller, and greener than those not living near the dead. By studying their size compared to other plant-life in the area, experts can determine where and when bodies were buried.
Insects, Rats, and Squirrels Help Determine Date of Death
I’ve written about entomology before, but did you know scavengers — like rats and squirrels, for example — prefer different types of human bones? It’s true. Rats like their bones greasy, and tend to chew on the ends in order to gain access to the marrow. Scientists can then look for these signs to determine how long the body has been in its earthly grave.
Conversely, squirrels prefer drier, more brittle bones that have been fully exposed to the elements. They use the calcium in bone to aid in the breeding of strong litters. By examining the different bite marks and narrowing when the bites occurred and by whom, forensic anthropologists are then able to determine if the body was skeletonized while fully exposed to the elements = squirrel activity. Or if buried in a shallow grave with nibbles on the ends of the bones = rats. Also, they can estimate how long the body has been dead and if the body has remained undisturbed.
Quick fun fact: it takes vultures only a few hours to strip a body down to bare bones — a time frame previously estimated to be weeks.
Sue Coletta—July 2, 2018
Bloodstain Pattern Analysis is the forensic interpretation of human blood evidence in crime scene investigations. It’s used to recreate actions that caused the bloodshed. Because blood has chemical properties that behave according to specific laws, trained analysts can examine the size, shape, and distribution of bloodstains to draw conclusions of what did—or did not—happen.
Bloodstain Pattern Analysis (BPA) applies the sciences of anatomy, biology, chemistry, mathematics, and physics to answer questions like:
Where’d the blood come from?
Who’d it belong to?
How’d it get there?
What caused the wound(s)?
From what direction was the victim assailed?
How were the victim and perpetrator positioned?
How many victims and perpetrators were there?
What movements were made after the bloodshed?
You’ve seen the CSI shows where investigators, dressed in their ‘bunny suits’, photograph drops, streaks, smears, and pools of blood, then swab for DNA and String the room back to Area of Convergence points. Well, that’s pretty much how it happens, except today most Stringing is done by 3D computerization.
Bloodstain pattern interpretation is nothing new. It’s been around two hundred years and became increasing sophisticated as technology advanced. I’ve been involved in a number of BPA examinations during my time as a cop and coroner. One that really stands out was when Billy Ray Shaughnessey axe-murdered his ex-girlfriend and her new lover. The room looked like a bomb went off in a red paint factory. I’ll tell you more about it at the end of this article. First, let’s look at how blood behaves.
Blood has three components that are suspended in plasma.
Erythrocytes are your red cells that transfer oxygen through hemoglobin. It’s what gives blood the red color. Leukocytes, your white cells, are your body’s defenders and support your immune system in fighting infection and disease. Platelets are formed in your bone marrow and play a major role in hemostasis or plugging up breaches in vessels.
Blood composition is about 55% plasma and 45% formed elements, or cells, which remain suspended due to agitation caused by your circulatory system. That’s called viscosity—it’s density or internal friction. Once blood leaves your body’s pressurized containment, it’s subject to the forces of gravity and surface tension which dictates its resting shape. That can be in drops, streaks, or pools.
Crime scene bloodstains take different forms due to factors like velocity and distance of travel, amount of blood flow, angle of impact, and type of surface or target it lands on. There are eight categories of bloodstain patterns:
Single Drop — These stains are typically from a vertical fall and under low velocity, like when your cut your finger and blood drips to the floor. Blood molecules are very cohesive. They attract and bind in a surface tension that makes a sphere. The drop stays in a ball until it strikes an object or a force acts on it. This is called bleed-out.
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This time I’ll let the original posters pose the questions:
Lisa Black—“Do you use problems in your character’s workplace to further the plot, and how?”
Sue Coletta—“Have you found a fascinating forensic technique in your research? Did you use it in a story?”
Garry Rodgers—“Have you used bloodstain pattern analysis in your works? Have you researched this science arm?”
