Anthropology & Forensic Science: Results of 394 Experiments

It is my great pleasure to share the results of the ANTH 394 experiments, conducted by students this summer on topics related to Forensic Anthropology at the University of Victoria.

We were very busy procuring dead animals and animal parts from local butchers, and one specimen even came from the fridge of a Wildlife Veterinarian for the province of BC. We spent some time talking about hazards and set up some Health & Safety protocols, then each student prepared a doable project within the time limits of our (very short) 6 week course on a related topic.

The purpose of this study was to give students an introduction into the process of conducting research. But as those of you pursuing science know, it is impossible to prepare for everything; and so, this exercise was also a lesson in addressing unexpected problems in field research, overcoming challenges, and realizing the limitations of the study.

Here are some of the incredible results:

Brittany by far had the most involved project in terms of health & safety. She looked at the effects of hydrochloric acid to (1) dispose of bodies and (2) to eliminate evidence of sharp force trauma. Brittany had her friend hit elk bone with a machete, then she drowned it in HCL, set up a go-pro camera, and watched the magic happen. Here is the result of the 1000's of pictures she took every minute for 24 hours:

In the end, it took more than 24 hours for the femur to dissolve, and somewhere between 48 hours and 5 days the entire elk bone was consumed, leaving nothing but a fatty film floating near the top of the remaining HCL liquid. Yuck.

After 24 hours pic (obvious changes in size and integrity!)

Photo credit: Brittany Walker

Sydney and Kayla studied stab wounds to determine what class characteristics could be gleaned to match a tool type to their trauma. Sydney compared markings made by three common household knives: a boning knife, chef's (or butcher) knife, and serrated (bread) knife. She stabbed pork ribs bought locally from a grocery store. Her only mistake was purchasing side ribs -- which she had to replace with some baby backs - since as you know, side ribs contain mostly cartilage (not bone!). Here she is hovering over the body to deliver the classic aim-for-the-heart knife wound (x30!!). I especially like her attention to safety/contamination by wearing goggles and gloves:

Sydney's results were super cool. She was able to see some beautiful textbook kerf marking (shape of the blade etched in bone), and photographed them under a high powered magnifying microscope (courtesy of UVic's Biology department) to produce evidence of puncture wounds, incisions, and hinge fracture.

Left Photo: Incision, as a result of the knife scraping/grazing the bone, the wound is longer than it is wide.

Right Photo: V-shaped puncture wounds that indicate the width & shape of the blade.

Both photos below: Hinge fractures that indicate direction of force. The first photo on the left shows that the blade perforated the other side and is a good example of a point of impact.

Photo credit: Sydney Edmondson

Kayla was the only student who analyzed trauma on human bone. Her blind study of stab wounds on a commingled sample yielded an MNI of 2. The fragments were put together from the forensic collection at UVic (on loan from UTennessee). Lucky for Kayla, she found a blade tip embedded in a skull fragment of the parietal bone. The placement and number of stab wounds led her to determine that the manner of death was homicide. In the end, both Kayla and Sydney realized how difficult it is to ascribe individualizing tool characteristics from bone fractures, even when controlling for the tool types!

Meaghan's experiment compared thermal injury patterns in bone and teeth at four temperatures. She wanted to see what heat would do to bone in varied temperature settings using an oven, charcoal BBQ, and a scientific kiln (as a proxy for crematorium). Another variable in her study was to see if there were any differences in heat signatures between fresh and frozen bodies. Her most interesting result was that the frozen sample lost more weight and became calcined more quickly (210 minutes) than the fresh specimen (which took 40 minutes longer!), and surprisingly at a lower temperature (750 degrees Celsius vs. 815) in the kiln. I guess this means that if you are looking to dispose of a body by fire, you won't have to wait as long if the body is frozen first.

Photo credit: Meaghan Efford-Lynch

Kaitlin studied gunshot wounds (GSW) in three animal skulls to determine path of the bullet, range of fire, velocity, and firearm type. She was only able to tell bullet trajectory in 2 of her 3 specimens from beveling patterns and a classic keyhole entrance wound. From the radiating and concentric fractures, Kaitlin was able to infer dissipation of force through her target, but learned that it is very difficult to match the width of a GSW to a bullet caliber and type, and even harder to a specific firearm.

Vanessa put a lot of thought into her project design of decomposing bodies in bagged versus soil environments over a 24-day period. She clothed 8 tiny mice, wrapped 4 in individual garbage bags, and buried 4 more directly in soil, arranged by popsicle-stick grave markers. She methodically removed one bagged, and one buried body every 6 days to compare the rate of decomposition. As expected, the mice bodies passed through various stages of rigor, livor, and algor mortis. The uncovered bodies dried out and mummified within the month, whereas the bodies wrapped in plastic had a more slimy appearance of soft tissue and organs, as a result of heat and moisture retained by the bag, which I bet was pretty smelly! Below are the comparative images from her study. Next time, Vanessa would like to bury bigger bodies and extend the duration of the study, but she may have to move from her backyard to a larger study site.

Day 6. Buried body (left), Bagged body (right)

Day 12.

Day 18.

Day 24.

Photo credit: Vanessa Tallarico

Matt and Mitch both studied fracture patterning from blunt objects. Mitch's study compared the difference between defensive wounds made by a hammer and a wooden club, while Matt conducted a blind study of blunt force skull trauma and enlisted his wife to both choose a weapon and hit a target. Matt wanted to see if he could tell what weapon she used. Thankfully, she made a video....

Wowzers. Yes, there was a hiccup in obtaining a fresh specimen: Matt's original idea was to use a fresh sheep's head and to deflesh by dermestid beetle population, but it was the wrong time of year for slaughtering sheep! Both Mitch and Matt realized the difficulty in matching a specific object to the observable fracture patterning, particularly since a variety of weapons can cause blunt force trauma, including a fall from a great height. In Matt's study, the only clue was a black smudge above the eye orbit, transferred from the weapon and onto the skull; material that can be used to individualize evidence. In the end, Matt could only describe the fractures as related to blunt impact, but seeing this item in his pantry probably should have tipped him off:

Photo credit: Matthew Branagh

I have to say, Mariana and Tara committed themselves entirely to this project, and I was quite impressed with their efforts. Both studied the rate of decomposition in fresh remains. In order to document changes effectively, they visited their study site every morning for 14 days. The study site had no bus access, so they shared the cost of renting through a car-share program and their results certainly paid off!

Tara compared the decomp changes between open-air and closed-air containers. She secured her open-air subadult pig leg from scavengers by placing a wire grate over top, and weighting it with a tire. Her air-tight tupperware container was secured with duct tape, but it was no match for local raccoons, who meticulously removed the tape to enjoy a snack. Thankfully it was already day 12 of her maceration study, so she processed the remains in the lab, but unfortunately no carnivore markings were found. She says that next time she will secure the closed air container to something permanent.

Photo credit: Tara Fraser

Mariana's study had the most surprising results of them all. In her study of the fly-life cycle she observed just about every other insect EXCEPT for maggots! An aggressive swarm of yellow jackets, several banded burying beetles, and one very determined hornet feasted on her buffet of muskrat, preventing the blow-flies from laying their eggs for 6 whole days! In a real forensic case, this kind of entomological evidence would have led investigators to underestimate time since death by almost one week. Even when the larvae were laid, ants carried away their bodies whole. It was an exciting and important discovery. I was particularly impressed that she identified all of her insects by taxonomic classification.

Photo below: The muskrat secured by wire and overlaid with a heavy tire to deter scavengers - and it worked!

Aggresive yellow jackets that feasted on flesh and probably the maggots as well!

Banded Burying Beetles that removed flesh from the underside of top layer of skin.

Day 6, finally the babies are born! Although I think Tara's yelp at the end is my favorite.

Day 14, The buffet had closed and not much was left, but the top fur layer of the dermis which started to blow away in the wind.

Photo credit: Mariana Astrid Núñez Silva

I must also THANK Becky Wigen, Senior Lab Instructor in our department who not only engaged the students in thoughtful discussions of their research questions, but also supervised them in the lab and even offered up her own backyard for Mariana and Tara to conduct their study.Thank you Becky! We could not have done it without you!

And so the curtain closes on another summer course. I really can't say enough wonderful things about the quality of work that these students have produced. Well done. I am definitely looking forward to teaching this class again, the bar is set high!