Forensic Taphonomy - Identification of Chemical Biomarkers for Forensic Medicine
Dr. Jonathan brooks completed his bachelor's science degree in forensic science at Teesside University, where he undertook his dissertation in conjunction with Durham Police Dog Unit investigating the chemical odor profile of blood in the intent to improve the accuracy and efficiency of blood detection dogs. He then went on to complete his doctorate in chemistry (with forensic applications) from the University of Leicester, investigating the volatile organic compounds (VOCs) expelled from and around decomposing specimens, with the intent of developing greater training aids for cadaver dogs as well as the creation of a more accurate method of determining post - mortem interval (PMI) . During his Ph.D., he lectured at numerous universities both nationally and internationally in specialist forensic subjects (Forensic Taphonomy ), but also around the presence of specialist forensics at the scene of crime Jonathan delivers specialist forensic capabilities around the search and recovery of human remains, which includes the delivery of training and consultancy to law enforcement agencies both to UK home office band international law enforcement agencies.
The session was started with the huge imminence of our speaker, Dr. Jonathan Andrew Brooks. After sharing is vast experience in the forensic taphonomy field he started the session with a short introduction about forensic Taphonomy.
Forensic taphonomy is an area that explores all avenues of decomposition stages and buried remains along with how a forensic expert approaches these cases during a criminal investigation. It also deals with the paleontological preservation of dead remains for future needs. Its forensic application includes identification of volatile organic compounds detected by the cadaver dogs for victim recovery, looking for biological markers for a better method of post mortem interval also known as time since death, and many more.
In Dr. Brooks's opinion, Forensic Taphonomy binds the field of Forensic Pathology, and Forensic Anthropology together. Looking from Dr. Jonathan's aspect he is more interested in looking at what the reaction mechanisms occur during decomposition as he told that if we start to understand the reaction mechanisms we then start to look at unique biomarkers and how that really contributes to our understanding of whether we can actually determine the time and stuff and what other chemicals that cadaver dogs are indicating too.
There is a process with lengthy super vital reactions which happened during algor mortis, rigor mortis, livor mortis. If we see the Stages of decomposition, there are fresh, bloated, active, and advanced skeletal decomposition stages and all through those processes of qualitative reactions that happen but as a chemist sometimes you aren't able to visually see what's actually happening and that's why our speaker find this subject usually fascinating because actually by instrumentation we can explore the degradation portion process in a lot more detail.
Now when we look at the kind of simplistic view of how the body decomposes we have to go back to a very basic chemistry reaction mechanism. We can see the different reaction mechanisms depend on the environment in which they degrade. As the body starts to degrade, there are alternative reaction mechanisms depending upon oxygen availability. So we can see as a result of aerobic degradation of glucose we have CO2 and water as a product whereas alternatively when we have a deprived environment of oxygen the products formed are esters and alcohols.
There have been a large variety of these different types of proteins, fats, and carbohydrates, which start degrading and how can we actually build these blocks to understand how the body decomposes.
So dealing with the decomposing body we should understand 2 basic things
1) Cadaver Dog Training
Dr. Jonathan worked with Cumbria Police Force and they were looking at establishing whether you could train cadaver dogs both on land and water. These dogs have the skill to indicate the remains underwater as well as on land and they were looking at what kind of train aids they would be using and how they were actually storing them and how what the training process and Dr. Jonathan's part was in terms of the kind of advising in terms of chemical variation that they take place. They were absolutely brilliant in terms of their training and attitude and kind of learning but it first demonstrates that there must be a common denominator within these samples for these dogs to detect and so they are now fully trained dogs that can detect underwater and on land which is incredible but from a chemistry point of view we're looking that knowing what is that they're indicating to. Is it a series of chemicals that are similar or are they varying in nature? And that's what is Dr. Jonathan's whole research field.
2) Post- Mortem Internal (PMI) (time since death )
As a forensic practitioner, this is a kind of the golden question that how do we approach this with such variations in the environment in which bodies are found, along with the current techniques, entomological approaches, life cycle of blowfly, and all the decomposition stage. Now if we see that how the body decomposes, there are extraneous variables that control and affect the process of decomposition such as the medium in which body is decomposed, what kind of insect activity is there and so many variables on which the process of decomposition depends. But the question is how we can measure this? So let’s know some methods in further;
Laboratory controlled experimental method :
Laboratory controlled conditions to measure the gaseous products from a decomposing cadaver using pig specimens as a human analog. Firstly by sealing the pig specimen into a 220L seal drum placed on a set volume of soil inserting a set volume standard gaseous mixture into the barrel. As it starts to degrade those gases are then emitted and transferred across the heated line into an anticoagulant instrument from there they were able to extract the volatile organic compounds using solid-phase microextraction and then desorb using SPME. the observation should be measured after 14 days.
There are a few fundamental things that should be kept in mind while performing this experiment
- The temperature-controlled laboratory
- The topsoil used for experiments should be of maximum depth of 2 M of Clandestine graves
- Set a flow of gas over the carcass with internal standard, bromobenzene such as in aerobic surface there should be zero air and ISTD whereas in Anaerobic surface there should be oxygen-free N2 and ISTD
- Collection of the specimen should be on the same day
- There should be no insect activity after the collection
- There should be no clothing present
- Triplicate the sampling every day for 14 days
- Humidity should be controlled in a small enclosed area with a large amount of soil
On looking at the graph it was fairly consistent for both experiments where the green line indicates aerobic and the red line indicates anaerobic. Now if we look at the qualitative change which occurred during the 14 days in this experimentation we will see
- Rupturing of the abdomen region as some of the intestinal tissue comes out of the stomach.
- Green discoloration across the specimen due to sulphur and hemoglobin addition or amino acids like phenol alanine reaction with oxygen. Whereas when we look at the anaerobic specimen there should be this green discoloration present over the specimen surface.
So for an overall view, we can see from the graph which is showing the variance in the compounds present across the decomposition period. In this graph we can see here is looking variation according to the day. On days 1 to 3 there is not much variation however on days 4 and 7 there is a large spike of a biochemical reaction. Interestingly after day 7 there is similar fashion can be observed as in days 1 to 3. on the other side When we see the anaerobic specimen from day 1 to 3 is similar to the aerobic specimen but on day 11 to 14 there is an additional variation is observed
After briefing the lecture our speaker discussed some important pinpoint which are as follows
- Variation in the sulphide concentration suggests oxygen is a key factor in the degradation process and suggests that other biochemical reactions may take alternative reaction pathways as a result.
- Variation in the presence of compounds at specific time periods (speculated from the PCA plots ) suggests two different types of odor profiles.
- Much of the samples that cadaver dog handles use are aerobic and never replicate anaerobic environments.
- For application to the criminal investigations, the cadaver dog handlers asked to train on buried remains more often to ensure the scent is detected.
It was really a great session we often came to know how cadaver dogs can help in identifying the dead remains. It was an insightful and knowledgeable session by Dr. Jonathan, there are few important point which I have found essential and most interesting to conclude this amazing session
- Different environments from laboratory-controlled decomposition show a variation in the compounds present.
- Training aids for Cadaver dogs aren't fully representative of the whole they are searching for end therefore protocols must be in place to ensure that they have a range of odor profiles to train on.
- Sulphide plays an important role in the implication of a new estimation of time since death however the effect of which extraneous variable has on the decomposition process must be investigated
If you are interested to know more about this session in detail you can visit the youtube channel forensic365 for the session recording.
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