World of Forensics: Forensic Chemistry and Taphonomy

By Madii Hussain, (UK) Biologist


Interviewee:

Bridget Thurn (AUS)

BForSc in Applied Chemistry

BSc (Hons) in Applied Chemistry

Expertise: analytical chemistry, gas chromatography, mass spectrometry, and organic synthesis.


Today, I’ve been given the pleasure of sharing an up-close and personal insight into the world of forensics with forensic chemist, Bridget Thurn. Bridget discusses her passion for forensic chemistry and taphonomy, how the process of death (for her) has changed from grim to beauty and the science behind decomposition.


About Bridget


Bridget recently submitted her thesis for a Bachelor of Science (Hons) in Applied Chemistry. Her honours thesis was conducted under the supervision of Dr Maiken Ueland and Dr Eline Schotsmans. It was based on profiling volatile organic compounds (VOCs) from human remains covered with lime and gypsum, which was completed at the University of Technology, Sydney (UTS). Furthermore, Bridget will be commencing her PhD in November 2021, under the supervision of Dr Maiken Ueland and Prof Steven Su, where she will be investigating detection methods for victims of mass disasters.

"My journey would not have been possible without the support of my lab group: Dr Maiken Ueland, Prof Barbara Stuart, Amber Brown, Sandali Alahakone, Alisha Deo, Sharni Collins, Zacchariah Knobel and Samara Garrett-Rickman."


1. What was your typical day like as a forensic chemistry Honours student?


“My days varied a lot as an honour’s student. If I was collecting samples, I would need to be at the field site at 9 am. My research took place at the Australian Facility for Taphonomic Experimental Research (AFTER). Sampling would usually take a couple of hours, and I would often drop my samples back at UTS after finishing. I used sorbent tubes to take headspace samples of decomposing human remains over the course of the decomposition process. If I was running samples, I’d get to university at 9 am, check that the instrument was working correctly, and put on as many samples as I could. I used comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) to detect the compounds produced by the remains. This meant that I could compare the results between donors across the stages of decomposition. I also spent many hours looking at an excel sheet processing my data, which was actually a lot more fun than it sounds.”


2. How does forensic chemistry/taphonomy impact your day-to-day life and mental health? And how do you deal with desensitisation?

“Forensic taphonomy has greatly impacted my life and I think it’s hard to work at a facility like AFTER without being affected by it in some way. Working at AFTER can be challenging, as within the Western world we are rarely confronted directly with death. Western funerary practises hide the dead and are performed away from the public eye. Therefore, when you first see the process of decomposition it can be quite jarring. In terms of desensitisation, I think once you understand the process of decomposition and know what to expect, it becomes easier. However, the weight of the work and the invaluable contribution of the donors is never lost on us. Seeing decomposition has definitely changed the way I think about death and by association people. I used to think of death as incredibly sad and final, which it is, but it’s also a beautiful process. Decomposition is very graphic; the body first bloats and then releases fluid and is constantly surrounded by insect activity. But after all the chaos the remaining skeleton is very peaceful. It’s definitely a privilege to be able to see the process.”


3. How important is forensics, in general, within a policing investigation?


“Solving investigations without forensics would be difficult, as you would have to rely heavily on witness testimony which is famously unreliable. The advancement of technology, especially in DNA fingerprinting, has been key in solving crimes. In terms of forensic taphonomy, research into VOCs produced through decomposition is quite a recent field and is very useful in the detection of human remains. Using forensic chemistry to gain an understanding of decomposition can aid in time-of-death calculations and victim recovery, and thus aids in police investigations and subsequent prosecutions.”


4. What inspired you into a career within forensics?


“When I tell people that I study forensics, most people think I grew up watching CSI or Law and Order and that’s what inspired me to get into the field. In reality, I chose my degree on a whim as a teenager because I thought it sounded interesting and I’m very lucky that I enjoy it so much. Although I enjoyed examining physical evidence, my favourite aspect of my degree was the application of chemistry in forensics, such as in toxicology and drug analysis. When I was choosing an honours project it was really important that it had a good basis in chemistry, because that was the side of forensics that I wanted to pursue.”



5. Within your expertise, can you tell us a bit more about the process of decomposition and the kinds of chemicals you look out for?


“My knowledge lies in the chemistry surrounding decomposition and the release of VOCs from decomposing human remains. There are two chemical processes involved in decomposition, which are autolysis and putrefaction. Autolysis is the process of intracellular self-digestion and begins immediately after death. Once oxygen is no longer being replenished, carbon dioxide levels begin to rise within the body’s tissues. This creates an acidic environment and causes intracellular membranes to rupture. This releases digestive enzymes into the cytoplasm, which begin to digest the cell’s outer wall. Autolysis ends with the release of proteins, lipids, carbohydrates, and nucleic acids from within the cells. Putrefaction follows this, by which these macromolecules are biodegraded by bacterial enzymes. Putrefaction causes the release of VOCs, which produces the characteristic skin discolouration and bloating due to gas and fluid build-up. The release of VOCs is also dependent on tissue type, with fat, for instance, decomposing to form fatty acids, which further break down into aldehydes, ketones, carboxylic acids, and short-chain alcohols. This knowledge is applied to aid in the recovery of missing persons, as cadaver dogs rely on the production of VOCs to locate human remains. Detection dogs are trained with decomposition fluid, blood, and human tissue so they can learn to identify the VOCs that are produced from human decay. In my research I found chemical compounds from many different classes, including alcohols, sulphur-containing compounds, hydrocarbons, and esters to name a few. The compounds produced are highly dependent on many factors, including the decomposition environment and the stage of decomposition. In terms of specific chemical compounds, dimethyl disulphide and dimethyl trisulphide are important as they are biomarkers of decomposition and are known to attract carrion insects to decomposing remains.”


6. Do you have any advice for future forensic scientists/chemists?


“I think my biggest piece of advice is to pursue what you love. If you find a topic interesting, then pursue that interest and read as many papers as you can find. Also go to lectures, and don’t be afraid to ask as many questions as you need to. I really started to love chemistry when I started to understand it and that came with asking my professors lots of questions and reading lots of papers. I think anyone can be good at anything as long as they find it interesting enough to research.”


 

Bridget has demonstrated that you can turn anything you’re interested in, into a long-term career. Her passion for forensic chemistry and taphonomy shines clearly throughout this interview and I hope that by sharing Bridget’s story, you are inspired to follow your own passions.


If you would like to get in touch with Bridget or me, then feel free to DM us on our twitter handles- @bridget_thurn @MadiiJH