radiocarbon dating

Forensic science is always evolving to better aid in the apprehension of criminals. What if a killer leaves his victim with no fingertips, DNA, or teeth? One way to determine the age of a victim is by examining their eyes.

Sounds bizarre, doesn’t it? The soulless eyes of a murder victim allow investigators to determine their age at the time of death. This process is called Radiocarbon Dating.

You’re probably familiar with how to tell the age of a tree by examining a split piece and counting the number of rings. Same basic idea when examining a victim’s eyes.

How is this possible?

Each of us, whether we realize it or not, have been exposed to naturally occurring levels of radiation. Most prominent in the 1960’s and 70’s, particles of radiation released into the atmosphere while testing nuclear weapons. Over the years — decades — these particles have fallen to trace proportions. However, there still remains naturally occurring levels of carbon in the air. Different forms of carbon are ingested every day, introducing trace elements into our system. Many carbon compounds are crucial to our way of life. Others are toxic (like cyanide, a carbon-nitrogen bond).

Radioactive particles and naturally occurring carbon settle in the crystallins of the eyes, and Radiocarbon Dating is the process of detecting this manifestation.

What are Crystallins?

Crystallins are microscopic proteins that bind together and collect on the lens of the eye. According to Explore Forensics (one of my favorite sites), crystallins got their name because of how they react under a microscope – like crystals, allowing light to pass through. From the time of conception (conception! Let that sink in…) until age two, these crystallins form in and around the lens of the eyes. At which point the formation stops. When this happens, trace elements of carbon permanently fuse in between the crystallins.

So, when an investigator – usually a scientist or pathologist – conducts a Radiocarbon Dating examination, they’re looking at levels of the carbon fused with the crystallins. To calculate age, they subtract the current levels of radioactive carbon in the eye from the naturally occurring levels of carbon in the atmosphere today. By comparing the levels of radiocarbon in the crystallins to the atmospheric levels they can determine the precise year of a victim’s birth.

Cool, right?

Determining the Sex of a Skeleton

There are many differences between the two sexes, and the variation runs as deep as our bones. This is especially important for corpses in advance stages of decomposition. All that might remain is the skeleton, perhaps teeth, and possibly some hair. Even if the pathologist has teeth and hair to work with, that doesn’t mean enough material remains to ID the victim’s sex

This is where the skeleton offers more information. The only exception would be that of a pre-adolescent, where sexual dimorphism is slight, making the task much more difficult.

The most common way to determine a skeleton’s sex is by bone size. Not the most accurate, but it’s a starting point. For the most part, male bones are larger than female bones because of the additional muscle that increases on the male through adolescence and into adulthood.

Another good inclination of sex is the pelvic area.

The sub-pubic angle (or pubic angle) is the angle formed at pubic arch by the convergence of the inferior rami of the ischium (loop bone at the base) and pubis (top of loop) on either side. Generally, the sub-pubic angle of 50-60 degrees indicates a male, whereas an angle of 70-90 degrees indicates a female. Women have wider hips to allow for childbirth.

Subpubic_angle,_male — Male sub-pubic angle

There are also distinctive differences between the pubic arches in males and females. A woman’s pubic arch is wider than a male’s as is the pelvic inlet, to allow a baby’s head to pass through.

The pubic arch is also referred to as the ischiopubic arch.
Incidentally, this difference is noticed in all species, not only humans. Same with Radiocarbon Dating.

The area around the pelvic inlet (middle of the pelvic bone) is larger in females than in males. A female skeleton who has given birth naturally will be identifiable because this space widens during childbirth. Even though it contracts afterward, it never fully returns to its original size. In the picture above notice the heart-shaped space.

Other Body Clues

The acetabulum — the socket where the femur (thigh bone) meets the pelvis — is larger in males. Also, the head and skull have several characteristics indicative of one sex or the other.

In males, the chin is squarer. Females tend to have a slightly more pointed chin.
The forehead of males slant backward, where females have a slightly more rounded forehead.
Males tend to have brow ridges. Females do not.

These differences and more tell the pathologist the sex of the deceased.

What Do Forensics and Skeletal Differences Have To Do With Writing?

Everything! Use the differences between male and female skeletons to add realism to fiction. Let’s say, a body is discovered in the blistering heat of the summer. The victim hasn’t been found for months, leaving only the skeleton. By showing the pathologist or Medical Examiner measuring the pelvic inlet, arches, and angles, we’ve essentially ensured our reader isn’t going anywhere.

Same holds true for the lab conducting a Radiocarbon Dating Test on the eyes of a murder victim. Adding forensic details is a lot of fun, too, for the writer and the reader. The trick is to disguise the research in a compelling storyline rather than dumping the information all at once.

Why is the hanging skeleton in doctors’ exam rooms always named Fred? Half the time they’re female. If they make me wait too long, I’m more apt to bring it to their attention. “Fred might need a new name, considering that’s a female skeleton.” And this always surprises them! They’re also less likely to leave me unattended for long in the future. 😉

By Sue Coletta

The forensic community works tirelessly to improve techniques to aid law enforcement, and much of this work is done at body farms across the country. The Texas body farm has conducted some amazing work. I’ve complied my top six forensic advancements, which I think you’ll find fascinating.

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.

Mosquitos Can Aid Investigators

In bodies that are badly degraded obtaining DNA becomes a chore, and sometimes isn’t possible at all. Researchers at the body farm, however, have a solution. Mosquitos and other biting insects, believe it or not, preserve portions of the DNA in the bodies they feed on. By trapping and dissecting these insects, DNA could be recovered.

How cool is that? It’s also a bit disturbing to think of mosquitos flying around with our DNA inside them. Or worse, when you smack a mosquito and it leaves a trail of blood, someone else’s DNA could be splattered on your palm. Yuck! I swear, the more I learn, the more paranoid I become. I don’t know about you but these things haunt me. LOL #writerslife

Decomposition Follows a Set Process

The body farm discovered a set pattern to decomposition. One week exposed to open air equals two weeks in the water and eight weeks buried underground. The latter refers to murdered victims, not people who’ve been embalmed or mummified. Environment, temperature, clothing, and weather all have to be taken into account as well, but as a baseline this formula aids investigators a great deal.

Drones Help Find Buried Remains

In bodies not visible to the naked eye, drone flights are part of an ongoing study using near infrared imaging to detect bodies above and below the ground. This technology can also spot locations, where a corpse was previously buried for up to two years after its removal.

“The search for clandestine bodies is a very time-consuming ordeal,” Wescott told the Texas Tribune. “Even then, a lot of times you can walk right by them and not realize that they’re there.”

As corpses decay, they release carbon and nitrogen into the soil, which decreases the amount of light the soil reflects. The influx of chemicals first kills plants, but as it disperses into the soil around the body it morphs into a fertilizer that reflects a ton of light. By using near infrared imaging the drones can detect these reflections. Two extremes show up as black and white on the mostly gray near infrared imagining. Anyone searching for a body doubles their chances of finding it.

Cool, right?

Have you found a fascinating forensic technique in your research? Did you use it in a story?

Wishing all of you a safe and happy 4th of July! Stay cool.
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Can they crack the riddles in time to save the next victim?

I’m excited to announce my new release, SCATHED, is now available for pre-order. Only 99c. Yay!!!

Killzoneblog.com

Tag Archives: radiocarbon dating

Eyes Reveal Our Age at Death