Forensics: Radiocarbon Dating & Skeletal Differences

Forensics: Radiocarbon Dating

Forensics, or forensic science, is always evolving to better aid in the apprehension of criminals. But 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 the 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.

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. But there still remains naturally occurring levels of carbon in the air. Different forms of carbon are ingested every day. Thus introducing the trace into our system. Actually, many carbon compounds are crucial to our way of life.

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 s/he’s looking at the levels of the carbon fused with the crystallins. To calculate age, s/he subtracts 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 s/he can determine the precise year of a victim’s birth.

Cool, right?

[tweetthis twitter_handles=”@SueColetta1″]#Forensics: Determining the age of a murder victim by their soulless eyes.[/tweetthis]

Determining the Sex of a Skeleton

There are many differences between the two sexes, and the variation runs as deep as our skeleton. 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 gender.

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 gender 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 gender 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.

Female sub-pubic angle

Female sub-pubic angle


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, where females do not.

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

[tweetthis twitter_handles=”@SueColetta1″]#Forensics: Determining the gender of a skeleton.[/tweetthis]

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

Everything! We can use the differences between male and female skeletons to add realism to our 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 our 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 our research in a compelling storyline rather than dumping the information all at once.

One of the things readers comment most about in reviews for Marred are the forensics. Specifically, the blood spatter analysis scenes, where Niko Quintano, Grafton County Sheriff, teaches one of his deputies how to determine low, medium, and high velocity spatter.

I’ve spent countless hours studying forensic science. The field fascinates me. As such, in the coming year not only will I set specific days for posts but I’ll share several forensic techniques and advances. Writers can use the forensic details in their stories and readers should find the posts interesting as well. Win win.


About Sue Coletta

Member of Mystery Writers of America, Sisters in Crime, and International Thriller Writers, Sue Coletta is the bestselling, award-winning author of psychological thrillers and mysteries. OOTG Flash Fiction Offensive magazine published her flash fiction and her short stories are published in numerous anthologies and collections. InSinC Quarterly featured her forensic articles about Radiocarbon Dating and Skeletal Differences. In 2017, Feedspot awarded her Murder Blog as one of the Top 50 Crime Blogs on the net. Sue's also the communications manager for Forensic Science and the Serial Killer Project. As a way to help fellow crime writers, Sue created a team of crime experts (detectives, coroners, police captains, etc.) and founded #ACrimeChat on Twitter. She's also a proud member of the Kill Zone, where she blogs every other Monday.


  1. I agree on crime fiction benefiting from certain fields of knowledge, be it coroner or doctor of pathology, private investigator, or police detective, to give some examples.

    I am fascinated by the easiness with which you, dear Sue, make it all seem one casual walk in the park, too. It is positive, and actually admirable!

    But the main topic of this article was about Eyes and the Time of Death. Made me instantly imagine a darkly humored, though slightly morbid, parody of Humphrey Bogart saying:

    ”I’m looking into your eyes, Darling…”

    • LOL
      Thank you for your kind words, Andre. I’m so glad you enjoyed this article. Actually, this article will be published in InSinC magazine, March issue. Exciting!!!

  2. This is fascinating!!
    Traci Kenworth recently posted…Writing Links in the 3s and 5…12/28/15My Profile

  3. Amazing details! Definitely a core component to depth and inspiration!!

  4. Men appear more Neanderthal than women. Men prefer to bludgeon victims while women prefer to poison food or slice flesh. Heh heh. Men are more likely to commit suicide by violent means, while women are more likely to overdose with drugs or open a vein with a razor blade. Not all men nor all women think and act stereotypically, and a good detective keeps an open mind.
    pauldaleanderson recently posted…Winning the numbers gameMy Profile

  5. Very cool. I had never heard of crystallins before. Any of these forensics details woven into a novel would add great authenticity.

    BTW, I couldn’t get your link to work for Explore Forensics. I’m going to Google it, but thought you might want to know.

    • Oh, thank you, Mae. I’ll fix the link. It’s an excellent site. The Explore Forensics link as well as many others are also in the Crime Writer’s Resource. Feel free to dig around.

  6. I was thinking you missed your calling and should have been a murder cop, Sue – then I stopped and realized you’re living out your calling as a writer.

    I didn’t know this about radiocarbon dating the eyes – always something new going on in forensics. This is an exceptionally well researched and written post – as always 🙂
    Garry Rodgers recently posted…ZAP YOUR APPMy Profile

    • Thank you, Garry! As you know I absolutely love forensics, which makes researching so much fun. Me as a murder cop? I’ve got plenty of buddies who are, does that count? Besides, as crime writers, we get to live vicariously through our characters. And, y’know, not deal with blood and guts.

  7. Always interesting stuff.

  8. This is really useful, as always, Sue. I find forensics interesting as it is. And if you’re going to write crime fiction, I think it’s important to have a good, strong sense of the way real-life police and other experts get this kind of information. That’s especially true if there’s no easy way to identify the victim.

    • Couldn’t agree more, Margot. If I could relive my life, I would definitely go into forensic science. That’s one of the things I love most about this writing gig. We get to live so many different lives. We can be a forensic investigator one day and a detective the next. Best job in the world!

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