Death

Maggot Analysis with Mass Spectrometry
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Maggot Analysis with Mass Spectrometry

A new proof-of-concept study by researchers at the University at Albany in New York has developed a mass spectrometry-based technique for the rapid species prediction of blow fly larvae for use in forensic investigations.

Entomological evidence (evidence relating to insects) has proven invaluable to forensic investigations for decades, particularly in the estimation of time since death. Insects which feed on decomposing remains, known as necrophagous insects, will colonise a body in a reasonably predictable pattern, with different insects arriving at different stages throughout the decomposition process. Different species of flies, beetles and mites are commonly encountered. Blow flies in particular will often arrive at the scene within minutes of death to lay eggs on the body. As these eggs hatch, larvae (or maggots) emerge to feed on the decomposing remains. By studying the type and age of insects present at a scene, it may be possible to estimate the time since death, or postmortem interval.

The ability to achieve this hinges on the correct identification of insect species, which is unfortunately not always straightforward. The larvae of different species of blow fly are visually very similar, thus difficult to distinguish by eye. For this reason, maggots are often reared to maturity for species identification, with adult blow flies exhibiting more distinguishing physical differences. Inevitably the rearing of maggots to adulthood is a time-consuming process that requires the expertise of a forensic entomologist.

In recent years, researchers have tried to develop more rapid approaches to insect species identification, particularly using chemical analysis. Researchers at the University at Albany in New York have been applying direct analysis in real time mass spectrometry (DART-MS) to the analysis of insect evidence to provide a rapid species identification tool. In DART-MS, the sample is placed between the DART ion source and the inlet of the mass spectrometer, allowing chemical components in the sample to be ionised and drawn into the MS for direct analysis. DART-MS requires minimal or no sample preparation and results can be obtained almost instantly. Using this technique, Rabi Musah and her team have already demonstrated the ability to determine the species of larvae, pupae and adult flies, highlighting a promising new tool in rapid species identification in forensic entomology.

However, until now this research has focused on the analysis of individual species. In a real-world scenario, maggots present on the body may consist of multiple different species, therefore any techniques developed for rapid species identification of larvae must be able to work with mixed samples. In a recent study, the team have taken the method one step further by examining the potential to identify larvae from mixed species.

Blow flies of various species were collected from Manhattan, New York. Maggots were submerged in 70% ethanol and the solution exposed to the ion source of the DART-MS to produce chemical signatures of both individual species and combinations of species. Mixtures of two, three, four, fix and six different species were analysed. Using the chemical profiles produced, a predictive model was constructed for the subsequent identification of unknown insect samples. Using this model, maggot species could be established with an accuracy of up to 94% and a confidence interval of 80-95%. Individual insect species are readily differentiated, with different species producing distinct chemical profiles. Similarly, mixtures of two different species could also be differentiated. As might be expected, samples containing a higher number of species were more difficult to differentiate.

Although only a proof-of-concept study and further validation is required, the study demonstrates that DART-MS could offer a way of rapidly determining the species of blowfly larvae, thus allowing investigators to establish which insects are present at the scene of a death and work out postmortem interval faster.

 

Beyramysoltan, S. Ventura, M. I. Rosati, J. Y. Giffen, J. E. Musah, R. A. Identification of the Species Constituents of Maggot Populations Feeding on Decomposing Remains—Facilitation of the Determination of Post Mortem Interval and Time Since Tissue Infestation through Application of Machine Learning and Direct Analysis in Real Time-Mass Spectrometry. Analytical Chem, 2020, In Press. 

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The Smell of Death: Confirming Decomposition using Volatiles in the Air

Odour mortis, or the ‘smell of death’, refers to the chemicals released from the body during decomposition. Renowned forensic anthropologist Arpad Vass, who has studied the chemical changes occurring in the body after death for many years, recently shared the details of a particularly interesting scenario. The article, published in the May 2019 issue of Forensic Science International, details a fascinating case in which the occurrence of human decomposition was demonstrated based solely on chemical compounds in the air for the first time, without any human remains actually being found at the scene. The article doesn’t specify suspect or victim details, but anyone familiar with the case will recognise it instantly.

First, a brief introduction. In 2008, a woman was charged with the murder of her daughter, allegedly storing the victim’s body in the boot of her car for several days before disposing of the remains and dumping the car. Police had initially been alerted to the incident by the suspect’s parents, who had picked up their daughter’s abandoned car and noticed a foul decomposition-like odour coming from the vehicle. Coupled with the fact they had not seen their granddaughter in several weeks, the suspect’s mother promptly called 911.

The police soon took possession of the car and agreed that the scent of decomposition was emanating from the vehicle. Numerous cadaver dogs, specifically trained to detect odours from decaying bodies, alerted to the back of the car, further suggesting some kind of decomposing remains had been stored in the boot of the car. Fly pupae were also discovered. Entomological evidence is frequently associated with decomposing human remains, with flies and various other insects known to visit corpses to feed or lay eggs. Although no human remains were found in the car, several weeks later the body of the missing girl was found in a wooded area near the suspect’s home, and the case promptly turned into a murder investigation, with the victim’s mother as the prime suspect. However with minimal physical evidence linking the body to the suspect’s car, law enforcement turned to a somewhat unconventional tool to aid their investigation.

Various pieces of evidence were recovered from the vehicle, including segments of carpet, scrapings from the tyre wells, and various pieces of rubbish found in the car. Interestingly, investigators also collected some air samples from the boot of the car. Air can be sampled from remote locations using a technique that utilises air pumps to draw in gaseous analytes from the environment and capture them in a sorbent trap. This collection of trapped compounds can then be transported to a laboratory for analysis. In this case, about 35L of air was collected from the vehicle into a type of sorbent tube, then analysed using gas chromatography/mass spectrometry (GC/MS). GC/MS is a well-established analytical technique, allowing scientists to separate the individual chemicals in a mixture and identify those components. You can read more about how mass spectrometry works here.

This process allowed researchers to figure out exactly which volatile chemicals were present in the suspect’s vehicle and establish whether these are everyday compounds likely to be found in a car, or if they had some other source.

In the years leading up to this case a great deal of research had been conducted at the University of Tennessee’s Anthropological Research Facility. At this facility researchers were investigating, among other things, the odours produced during the decomposition of a human body. The odours created during this process are the result of volatile compounds produced as the body decomposes, and research has demonstrated that hundreds of individual chemical components are formed during this complex process. As part of research at the university, researchers had constructed a vast database of hundreds of chemicals detected during the process of human decomposition, including the different decomposition stages at which those chemicals appear. By comparing the chemicals detected in the vehicle with those stored in the database, it was possible to identify compounds known to be produced during the decomposition process. There was an 80% match between the compounds detected in the boot of the car and those chemicals considered to be relevant to human decomposition. Furthermore, unusually high levels of chloroform were also detected in the boot of the car.

The results from the air samples collected and chemical extracts from various other artefacts in the car led the researcher to conclude that there was a very high likelihood of a decomposition event occurring in the boot of the car. Many of the compounds detected in the vehicle could only be logically explained by the presence of decomposing remains.

Despite these findings (and various other pieces of evidence presented in court), the jury reached a verdict of not guilty for the charge of murder. Not too surprising an outcome, considering the use of air analysis to detect decomposition had not previously been used in a legal investigation. However in closing arguments, the defence stated that the victim had in fact been placed in the vehicle for transport (claiming the victim’s death had been accidental), ultimately confirming the results of the analysis.

 

Vass, A. A. Death is in the air: confirmation of decomposition without a corpse. Forensic Sci. Int. (2019). doi:10.1016/j.forsciint.2019.05.005

Vass, A. A. Odor mortis. Forensic Sci. Int. 222, 234–241 (2012).

 

Tracking Movements with Fingernails
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Tracking Movements with Fingernails

When human remains are discovered, investigators will often turn to routine methods such as fingerprinting, DNA profiling and the use of dental records to identify the individual. But in the absence of database records for comparison, such traditional techniques may not prove all that useful, and forensic scientists must look for new ways to identify the unknown.

In recent years the use of stable isotope analysis has aided forensic investigations, particularly in establishing the geographic origin of unidentified human remains. Isotopes are different forms of an element. For example, oxygen has three naturally occurring stable isotopes: O16, O17 and O18.  These isotopes are incorporated into substances in the environment (such as water) in varying ratios. The relative abundance of isotopes can be influenced by various factors in a process known as isotopic fractionation. It has been found that isotopic ratios can be related to different regions of the world. For example, the tap water in one country may have a completely different isotopic signature in comparison to water in another country. How does this relate to the isotopes found in our bodies? Well, you are what you eat. As you consume food and water from a particular area, the atoms in our bodies express abundances similar to the food and water consumed.

This provides the basis for using isotope analysis to trace materials back to a certain geographic region. It has already been demonstrated that the isotopic analysis of bones, teeth and other bodily tissues can allow for individuals to be traced to particular locations, typically through the analysis of oxygen, hydrogen and sulphur isotopes. However last year, researchers at the University of Utah took a different approach, this time focusing on fingernails.

As with bones and teeth, the isotopic content of our fingernails will be affected by factors such as the food and water we consume. As fingernails are estimated to grow at a rate of 3-4mm per month, they are a prime target for studying isotopic patterns in an individual over a shorter timespan (less than six months as oppose to years). This is by no means the first study of isotope abundances in fingernails, but previous research has typically focussed on single timepoints rather than tracking the same individuals over time. As global travel becomes more commonplace, it is increasingly likely that human remains could have originated from any part of the world. Therefore, we need to understand how travel can cause changes in isotope abundances within the body.

This study aimed to establish whether fingernail isotope ratios were different in a group of local people in comparison to non-locals who had recently moved to the area (in this case Salt Lake City in the United States). Over a period of a year, fingernail clippings were collected at multiple timepoints from a group of volunteers, about half of which were local residents and the rest individuals who had recently arrived from various locations across the US and the world. The fingernail clippings were cleaned (to remove surface components and contaminants that could interfere with the analysis) and subjected to analysis by isotope ratio mass spectrometry (IRMS). IRMS is a particular type of mass spectrometry that allows us to measure the isotopic abundance of certain elements typically hydrogen, carbon, nitrogen, and oxygen. You can read more about IRMS here.

The isotope values of samples from residents were used to construct a baseline of expected values for the area, with isotope values from non-residents’ samples being compared with these. Initially, samples from non-residents showed a wide range of isotopic values, which is to be expected given they had only recently moved to the area. Some residents did fall within the expected range of locals, but these participants had moved from relatively nearby locations, which could explain the similar relative isotopic abundances. However after about 3 months, the fingernail isotopic patterns shifted until the non-residents could no longer be distinguished from the residents. This indicates that although the relative abundance of isotopes in our fingernails can shed some light on geographical movement, it can only provide information relating to the past few months. Inevitably there will always be a certain amount of error associated with such analyses, with variation from the likes of short-term travel and random dietary changes being impossible to account for.

 

Mancuso, C. J, Ehleringer, J. R. Resident and Nonresident Fingernail Isotopes Reveal Diet and Travel Patterns. Journal of Forensic Sciences. 2019, 64(1).

 

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Interview with Forensic Taphonomist Professor Shari Forbes

What is your current job role and what does this entail?

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Forensic taphonomist Professor Shari Forbes.

I am a Canada 150 Research Chair in Forensic Thanatology and the Director of the Secure Site for Research in Thanatology (SSRT). The SSRT represents the first human taphonomy facility in Canada and is the only place in this distinct climate where we can study the process of human decomposition through body donation. My role is to lead and conduct research at this facility, specifically in the field of forensic thanatology and decomposition chemistry. This role also involves engaging collaboratively with our external partners who can benefit from the research and training we conduct at the facility, notably police, forensic services, search and rescue teams, military, human rights organisations, and anyone involved in death investigations.

What initially attracted you to your particular field of research?

I have always had a passion for science and knew that I wanted to pursue a career in a scientific field where I could clearly see the impact of my work. When I was in high school, I enjoyed reading crime novels and probably understood what forensic science entailed better than most people (this was before the advent of CSI, Bones, NCIS, etc.!). My love of science combined with my interest in criminal investigations naturally led to pursuing a career in this field. At the time, there was only one university in Australia that offered a forensic science degree so the decision of where and what to study was relatively easy. Although chemistry wasn’t my strongest subject at school, I enjoyed the degree because it applied chemistry to forensic science and in this way, I could understand how my skills would help police investigations.

Can you tell us about the research you’re currently involved in?

My research focuses on the chemical processes of soft tissue decomposition and the by-products released into the environment. This can include compounds released into air, water, soil, textiles, or anything surrounding the body. The majority of my research at the moment focuses on the release of volatile organic compounds (VOCs) into the air to better understand the composition of decomposition odour. Although this is not pleasant work, it is very important to understand the key compounds used by cadaver-detection dogs for locating human remains. If we can identify the key VOCs and determine when they are present, we can enhance the training and success of cadaver-detection dogs in complex environments such as mass disasters.

You were heavily involved in the establishment of the Australian Facility for Taphonomic Experimental Research. What were some of the greatest challenges in this and how has the facility since developed?

It took approximately 3.5 years to establish AFTER from the day we started planning it to the day it opened in January 2016. I have since realised this is not that long compared to some of the other facilities that are currently operating but there were challenges and hurdles that we faced along the way. In Australia, establishing a human taphonomy facility essentially requires three things: 1) an organisation willing to lead and support it; 2) a body donation program; and 3) accessible land that can be used for taphonomic research. We were fortunate that the University of Technology Sydney (UTS) had these three things and we also had the financial and in-kind support of all of our partners including academic institutions, police services and forensic laboratories. Once we had this support and made the decision to proceed, we still needed to seek approval from our local council to use the land for this purpose; apply for funding to build the facility; and apply to have the facility licenced to hold human remains for the purposes of taphonomic research and training. Thankfully, everyone we engaged with was highly supportive of the facility and willing to work with us to ensure we followed all legislation and regulations. We also ensured we had a strong communication plan to raise awareness with the general public about the benefits of these facilities and how important the research is to assist in the resolution of death investigations.

AnnaZhu_UTSScience_1750

The Australian Facility for Taphonomic Experimental Research

Since opening, we have been amazed by the general interest in AFTER and the number of people wanting to donate their body. We have also increased our partnerships to benefit more police and forensic services as well as others services such as the cemetery industry. We are currently planning to provide more training opportunities, particularly relating to disaster victim recovery and identification, and to establish more AFTER facilities across Australia to better represent the diverse climates experienced across the country.

You recently left the University of Technology Sydney to relocate to Canada. How will your role and research be changing as you make this move?

I was honored to be the Director of AFTER and it was a difficult decision to leave Australia. However, I recognise the importance of these facilities and the need to establish them in other countries so when I was asked to open Canada’s first human taphonomy facility, it was an opportunity I could not turn down. My experience in Australia has already assisted greatly in establishing the facility in Quebec and we will certainly be able to open the facility much more rapidly as a result. Like in Australia, we hope it acts as a template for future facilities across Canada since this country also has very diverse climates. In reality, neither my role nor my research will change significantly. The greatest change will be the climate and its impact on the process of decomposition!

Finally, do you have any advice for young scientists eager to pursue a career in your field of work?

It sounds like a cliché, but I always encourage students to pursue a career in a field they are passionate about. If you had told me 20 years ago that I would being leading not one, but two ‘body farms’ I would never have believed it (especially after just reading Patricia Cornwell’s novel that gave these facilities that name!). But I knew I was passionate about studying a science that was deeply applied and had a clear impact on society. I had no idea where it would lead me or even if I would get a job in the field, but without that passion, I would not have been motivated to do any of the things I have done; namely: complete my degree, continue on with a PhD, do research in decomposition chemistry, and ultimately become an academic so that I could continue my passion of conducting forensic taphonomy research. So if you are going to do something for the next fifty years, make sure it is something you love doing!

Find out more on the Secure Site for Research in Thanatology website.

 

This is Part 17 of our series of interviews with forensic professionals. If you’re a forensic scientist (academic or industry) or a crime scene investigator and would like to be part of this series of interviews, get in touch by emailing locardslabblog[at]gmail.com.

Instant Insect Identification to Aid Forensic Entomology Investigations
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Instant Insect Identification to Aid Forensic Entomology Investigations

During the investigation of a suspicious death, entomological (that is, insect-related) evidence may be able to provide vital clues as to when the victim died. Determining time since death, or post-mortem interval, can be one of the most important aspects of such an investigation, so it comes as no surprise that a great deal of research has been directed towards improving these estimations.

Insects can play a huge role in estimating time since death. Various types of species of insect will often visit the scene of a death in a relatively predictive manner, either to feed on the decomposing remains (known as necrophagous insects), to prey on other insects present, or to find a suitable place to lay their eggs. Blow flies, a group which includes common flies such as the bluebottle and the greenbottle, are often of particular interest. Forensic entomologists will typically study the insects, eggs and larvae present at a death scene, utilising the type of bugs found and their stage of development to track back to the likely time at which they arrived, thus when the victim may have died. However in order to accurately do this, entomologists must often collect insect specimens for closer inspection and even to rear to adulthood in order to determine the exact species, which is evidently a time-consuming process requiring a high level of expert knowledge.

For the first time, researchers at the University of Albany have applied a technique called direct analysis in real time with high resolution mass spectrometry, or DART-HRMS for short, to the analysis of blow fly eggs. Published in the latest issue of the journal Analytical Chemistry, the technique has demonstrated the possibility of almost instantly differentiating between different fly species based on the amino acid profiles of the eggs.

DART-MS, developed in 2005 by Dr Chip Cody of JEOL, is an ambient ionisation mass spectrometry technique that allows for samples to be directly analysed without any time-consuming sample preparation steps, and perhaps most importantly without destroying the sample. The sample is simply presented in its native state between the ion source and the inlet of the mass spectrometer, enabling compounds present in the sample to be ionised and drawn into the instrument for analysis and identification.

dartms

Sampling interface of DART-MS. Source: Wikimedia Commons

During this investigation, researchers used pieces of pork liver to attract a number of different blow fly species before transporting them to the laboratory. The flies were reared until they lay new eggs, which would be the focus of the analysis. The study utilised specimens of a number of species, including Calliphora vicinia, Lucilia coeruleiviridis, Lucilia sericata, Phormia regina, along with specimens from the Phoridae and Sarcophagidae families. Even to the eye of an expert, the eggs of these specimens are often indistinguishable. The eggs were simply placed in an ethanol solution and the mixtures directly subjected to DART-HRMS analysis.

The technique focused on the analysis and identification of amino acids in the eggs, essentially enabling researchers to produce a chemical fingerprint unique to eggs of a particular species. Examination of the mass spectra showed that the different species exhibited a unique chemical fingerprint, and by using multivariate analysis it was possible to better visualise the similarities and differences between amino acids detected in the eggs of different species.

Unsurprisingly, many amino acids were common to multiple species. For instance, alanine, isoleucine and proline were detected in four of the species, whereas valine was detected in all but one of the egg samples. However some compounds were unique to particular species, and it is these unique amino acids that will prove to be most beneficial in differentiating between the eggs of different species. For instance, glutamine and tryptophan were only present in the eggs belonging to P. regina. Interestingly, the research also demonstrated the ability to distinguish between families as well as species, with some compounds only detected in the eggs of specific families.

By using this particular technique, almost instantaneous identification could be achieved. Of course this research has included only a very limited number of species, thus a much bigger investigation would be necessary before the technique would really be beneficial to a legal investigation. Not only would further species need to be included, but another potential development would be the production of a chemical profile database against which unknown insect samples could be compared. Developed further, the use of DART-MS could save investigators a lot of time in the identification of insects of forensic interest.

 

References

Cody, R. B., Laramée, J. A. & Durst, H. D. Versatile New Ion Source for the Analysis of Materials in Open Air under Ambient Conditions. Anal. Chem. 77, 2297–2302 (2005).

Giffen, J. E., Rosati, J. Y., Longo, C. M. & Musah, R. A. Species Identification of Necrophagous Insect Eggs Based on Amino Acid Profile Differences Revealed by Direct Analysis in Real Time-High Resolution Mass Spectrometry. Anal. Chem. (2017) In Press

 

Killer Cocktails: The Chemistry Behind the Lethal Injection
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Killer Cocktails: The Chemistry Behind the Lethal Injection

In many countries worldwide, including the United States, lethal injection is used as a humane method of executing a death row inmate. With the lethal injection, the life of the inmate can theoretically be cleanly and swiftly ended through administering a number of drugs, with no pain and minimal trauma.

The debate over the lethal injection hit the news again last month when the U.S. Supreme Court ruled against claims that the use of a drug used in lethal injections (midazolam hydrochloride) violates the Eighth Amendment (relating to prohibiting cruel and unusual punishment). Despite this method of capital punishment largely replacing supposedly less humane forms of death such as the electric chair and hanging, there is still great debate over the ethics of certain drugs used, and whether they actually do provide a swift and pain-free death.

But what drugs are involved in this lethal cocktail, and how do these end life in an apparently ethical manner?

The procedure for lethal injection can vary across different countries and even different states. In the United States, execution by lethal injection is typically achieved through the intravenous use of three drugs in succession, each with a different purpose, though in some instances a single-drug method is used, usually involving a lethal dose of anaesthetic.

Sodium Thiopental (Source: Chemspider)

Sodium Thiopental (Source: Chemspider)

But let’s look at the three-part cocktail. The first drug to be administered is usually a barbiturate to act as an anaesthetic (painkiller), used to ensure the remaining steps in the procedure do not cause any pain. Traditionally sodium thiopental is used, a fast-onset but short-acting barbiturate. Barbiturates are compounds which can ultimately produce anaesthetic effects. They act as agonists of gamma-aminobutyric acid (GABA) receptors, which are inhibitory neurotransmitters in the central nervous system. By binding to this receptor, the activity of the central nervous system is depressed, bringing about effects ranging from mild sedation to general anaesthesia. In this instance, a sufficient dosage is administered to render the inmate unconscious, thus ensuring a painless procedure. However some have argued that the fast-acting effects of sodium thiopental can wear off before the execution procedure is complete.

Succinylcholine Chloride (Source: Chemspider)

Succinylcholine Chloride (Source: Chemspider)

Once the inmate is unconscious, a neuromuscular-blocking drug is then administered, generally succinylcholine (also known as suxamethonium chloride) or pancuronium bromide. Compounds such as succinylcholine bind to acetylcholine receptors, blocking the action of acetylcholine, a neurotransmitter essential in the proper functioning of skeletal muscle. When succinylcholine binds to this receptor, a cation channel in the receptor opens and depolarisation of the neuromuscular junction occurs. Normally when acetylcholine binds to this receptor, it soon dissociates following depolarisation and the muscle cell will be ready for the next signal. However compounds such as succinylcholine have a significantly longer duration, ultimately resulting in paralysis. In short, administering a drug such as succinylcholine prevents acetylcholine from communicating with the muscles and thus paralyses the inmate’s muscles, including those used to breathe. Other drugs such as pancuronium bromide can also be used, which have a different mechanism of action but ultimately achieve the same final result of muscle paralysis.

Finally the salt potassium chloride is administered. Within the body a variety of salts are vital for brain function, transmission of nerve signals and the beating of the heart, and these salt levels are tightly regulated by the body. In the normal functioning of the body, the majority of potassium is confined to the cells, with very little being present in the bloodstream at any one time. The introduction of a large amount of potassium chloride disrupts this electrochemical balance as the body’s cell are not able to equilibrate, rendering the cells unable to function, leading to cardiac arrest. In simpler terms, the overdose of potassium chloride brings about a condition known as hyperkalemia, in which the potassium concentration in the body is too high, causing the heart to fail. The inmate is officially declared dead when a cardiac monitor indicates the heart has stopped.

Recently, the drug used to initially render the inmate unconscious, sodium thiopental, has been difficult to obtain for a number of reasons, thus some states in the U.S. have used midazolam hydrochloride, a drug which has ultimately caused a great deal of controversy in recent years, such as in the Clayton Lockett case. This benzodiazepine is commonly used as a sedative, but when used during the lethal injection procedure, it is generally combined with an opiate. This is because midazolam itself has no analgesic (painkilling) effect, thus an additional drug is required to achieve this. Despite its recent use, claims have been made that a number of executions using this drug resulted in the prisoners showing signs of consciousness and gasping, suggesting that they were not quite as unconscious as intended. If the inmate is not unconscious when the muscle paralyser and electrolytes are administered, they may experience suffocation due to the muscle paralysing agent and burning caused by the potassium chloride.

So there we have it – some of the primary drugs administered during the lethal injection procedure and how they react within the body to bring about death. For more information on the death penalty (namely in the U.S), visit the Death Penalty Information Center.

References

Johnson, B. A. 2011. Addiction Medicine: Science and Practice Volume 1. New York: Springer.

Kroll, D. 2014. The Drugs Used in Execution by Lethal Injection. [online] Available from: http://www.forbes.com/sites/davidkroll/2014/05/01/the-pharmacology-and-toxicology-of-execution-by-lethal-injection

Kemsley, J. 2015. Sedative for Lethal Injections Affirmed. [online] Available from: http://cen.acs.org/articles/93/i27/Sedative-Lethal-Injections-Affirmed.html

Cover Image Credit: Thomas Boyd (The Oregonian)

Diatoms and Death By Drowning
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Diatoms and Death By Drowning

A body is found floating in a lake, the circumstances surrounding the death a complete mystery.

One might assume the cause of death to be drowning, and for this there may be certain pathological indicators. But failing these indicators, how can you be so sure that the victim drowned? It could be that they were killed elsewhere, their body tossed into the lake to eliminate suspicion. Or perhaps they did drown, but in alternative circumstances in another body of water. The scenarios are endless. But how can these questions be answered?

The key to this problem might just be a diverse group of microscopic algal organisms known as diatoms.

Dia

Perhaps you’ve heard of them. These asexually-reproducing organisms exist in a vast variety of shapes, sizes and colours, plentiful in many aquatic environments and existing in a tremendous range of populations. A particularly important feature of diatoms is their silica-based cell wall, producing an especially distinctive appearance that can vary greatly between different species. This cell wall enables diatoms to be particularly resistant to decay, so they may persist in an environment for a long time. It is their abundance, uniqueness and resistance that has allowed diatoms to be of such great use in the field of forensic limnology, that is the study of freshwater ecology in a legal context.

So how can these minute microorganisms help determine the circumstances surrounding a suspicious death?

Imagine a person drowning. As the head is submerged, water is inhaled into the lungs, along with any microorganisms contained in that water. In this case, diatoms. So the presence of diatoms in the lungs proves death by drowning? Not at all. Water can passively reach the lungs regardless of whether the victim was dead or alive by the time they reached the water. However if the victim is alive, when diatoms hosted by the water reach the lungs, they will be circulated around the body via the bloodstream, being deposited in different bodily tissues and internal organs.

So with this in mind, the investigator may be able to conclude that cause of death is likely to have been drowning if these diatoms are detected in the internal organs. At this point it is necessary to note that diatoms may already exist within the body, as these algal communities are found in various environments other than water. It is therefore necessary to establish a kind of match between the diatoms in the suspected drowning medium and those inside the body of the deceased. By studying the species of diatoms present and their abundance, it may be possible to conclude whether the diatom populations are consistent with one another. Interestingly diatom populations can also vary seasonally, thus may be able to provide some insight into the time of year in which a victim drowned based on the diatoms extracted from the remains. Comparisons such as these can be made by collecting water samples and extracting diatoms from bodily tissues and internal organs (often through acid extraction), before comparing the diatoms using light or electron microscopy.

The possible applications of the study of diatoms is by no means limited to these scenarios.

Dia2

Numerous features of diatoms make these microorganisms an ideal focus for analysis in forensic investigations. Their minute size means that they can be readily transferred from the crime scene by objects or people, with perpetrators unlikely to be aware of the presence of these organisms. The resilience brought about by the silica-based cell wall allows for them to persist in the human body even beyond later stages of decomposition, during which time cause of death by pathological means may be more difficult. The distinctive morphology of diatoms allows for species to be distinguished from one another, and their abundance and variation results in different bodies of water developing very distinctive assemblages of diatoms.

Unfortunately the use of diatoms as an indicator of cause of death by drowning is somewhat controversial, highlighting the need for further research in this area of study.

References

Horton, B. P. Boreham, S. Hillier, C. The development and application of a diatom-based quantitative reconstruction technique in forensic science. 2006. University of Pennsylvania Scholarly Commons.

Krstic, S. Duma, A. Janevska, B. Levkov, Z. Nikolova, K. Noveska, M. Diatoms in forensic expertise of drowning – a Macedonian experience. For Sci Int. 127(2002), pp. 198-203.

Pollanen, M. S. Diatoms and homicide. For Sci Int. 91(1998), pp. 29-34.

Scott, R. S. Morgan, R. M. Jones, V. J. Cameron, N. G. The transferability of diatoms to clothing and the methods appropriate for their collection and analysis in forensic geoscience. 241(2014), pp. 127-137.

Featured Image – https://www.flickr.com/photos/carolinabio/6622267417

From Mummies to Grave Wax – The Preservation of Human Cadavers
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From Mummies to Grave Wax – The Preservation of Human Cadavers

Warning: Graphic images included.

When we envisage the decomposition of a corpse, the images that probably come to mind are of a rapidly-decayed, foul-smelling body quickly turning to sludge and bones. But there are actually other pathways a body can take following death, some of which can be of great importance in a forensic investigation. I’m namely talking about mummification and adipocere.

Mummification

Thanks to the Ancient Egyptians, we all know about mummification, a particular process of body preservation. When these guys mummified their dead, this routine typically involved the removal of the internal organs, most notably the brain, which was pulled out through the nostrils. Finally, the body would be wrapped in linens and salt and left to dry. The end result would be a remarkably well-preserved body displaying features that would have usually been lost to decomposition.

Aside from this especially famous post-mortem ritual, there are actually a number of ways by which a body can become mummified. For instance, more modern intentional mummification would utilise chemicals to preserve the body. But how can mummification occur naturally, and what are the implications of this in a forensic investigation?

The natural preservation of a cadaver is highly dependent on the surrounding environment, with only very specific conditions causing the body to mummify. A range of factors can play a part in this phenomenon, including temperature, humidity and the action of bacteria and other microorganisms.

In hot, dry climates moisture can evaporate from the skin at such an accelerated rate that the process of mummification can occur. As the skin is rapidly dehydrated, it often takes on a dark and leathery appearance. The internal organs may be preserved to an extent, though will typically undergo some level of decomposition so are at least likely to be smaller in size. Hot, dry climates can also hinder bacterial growth, limiting the bacterial decay and further preserving the body. Hot, sandy deserts are perhaps amongst the first scenarios that come to mind when considering mummification, but mummified remains have also be discovered in attics, basements, and even within the walls of buildings.

Conversely, especially cold and dry environments can also bring about mummification. The cold temperatures can significantly slow microorganism activity, once again reducing the rate of decomposition and aiding in preservation. A famous example of this is the natural mummy Otzi the Ice Man, believed to have died thousands of years ago but preserved through mummification induced by extremely cold temperatures.

mumm1

Mummifying conditions are not limited to temperature-based factors. Environments of extreme salinity (salt content) can preserve cadavers. The majority of bacteria cannot survive in highly salty conditions, thus severely reducing microbial action on the body. Furthermore salt itself acts as a desiccant on the soft tissue, dehydrating the body and drawing out water much as high temperatures would. An example of this type of mummification was experienced in Iran, where a number of mummies were found in the Chehrabad salt mines.

Mummified remains have also been found in bogs or marshland, in which the excess water, organic material and anaerobic (oxygen-free) environment prevents a great deal of bacterial action, thus preserving the body. This is something of a contrast to the typical hot, arid conditions mostly associated with mummified remains, but bogs with particularly acidic water, low temperatures and a lack of oxygen can essentially pickle a body. Thousands of these “bog bodies” have been recovered over the years, perhaps the most famous being the Lindow Man, determined to be the victim of a prehistoric ritual killing.

The conditions described may not necessarily induce mummification throughout the entire cadaver, but in some cases may cause localised mummification, if only particular areas of the body are exposed to these conditions. Mummification most often occurs in the face, scalp, chest and back, but typically begins in the extremities such as the fingers and toes.

Adipocere

Another phenomenon that can assist in preservation of a cadaver is the formation of adipocere. Known as “grave wax”, this is a soapy, white or grey wax composed primarily of saturated fatty acids such as palmitic and stearic acid formed through the hydrolysis and hydrogentation of body fats (Forbes et al, 2005). Numerous theories have been put forward to suggest how adipocere forms, namely the saponification, hydrogenation and fat migration theories.

A cadaver presenting adipocere. Credit: Kumar et al, 2009

The type of environment required for adipocere formation is somewhat different from that suitable for mummification. It is often encountered in especially humid graves with little or no air access, thus oxygen-poor, such as a bog or certain bodies of water. The formation of adipocere can take weeks if not years to form depending on the climatic conditions, the rate at which it forms being further affected by the environment and circumstances surrounding the cadaver. Depending on the extent to which it forms, adipocere can produce a waxy layer across the body and act as a barrier against the usual process of decomposition, providing significant protection over time as adipocere itself is fairly resistant to decay.

So these are some of the alternative routes of decay a body can take post-mortem. But what does this mean to the forensic scientist?

In some cases, the occurrence of mummification or adipocere formation can be of assistance to a forensic investigation, as it may be possible that certain aspects of the deceased person’s appearance and even any injuries they might have acquired will be preserved. Mummified tissues can even be rehydrated to aid in visualising injuries and other distinguishing marks. Similarly, the formation of adipocere can preserve tissues and organs along with recognisable facial characteristics. This can in theory aid in identification if the victim is unknown or even determining cause of death.

Furthermore, just as the stage of decomposition of a body can roughly indicate the post-mortem interval (time since death), mummification and adipocere can provide some indication in that a certain amount of time is required for mummification to occur. Approximately 6-12 months are required for the natural mummification of an adult, with a child’s body requiring less time to become mummified (Gitto et al, 2015), though in some cases mummification has been reported in a matter of weeks or even days (Sledzik and Micozzi, 1997). Of course these time periods can vary widely depending on climatic conditions and a number of other factors, but they may provide assistance nonetheless. To an extent it may be possible to determine the rough age of the remains based on the weight of the mummified cadaver, as more recent bodies will be heavier than those which are older and have lost a greater proportion of water content.

So given the right conditions, processes such as mummification and adipocere formation can interestingly be a great aid to the forensic investigator.

References

Bereuter, M. T. L. Lorbeer, E. Reiter, C. Seidler, H. Unterdorfer, H. Post-morten alterations of human lipids – part I: evaluation of adipocere formation and mummification by desiccation. Human Mummies. 3 (1996), pp. 265-273.

Bryd, J. H. Castner, J. L. 2010. Forensic Entomology: The Utility of Arthropods in Legal Investigations. Boca Raton, Florida: CRC Press.

Forbes, S. L. Bent, B. B. Stuart, H. The effect of soil type on adipocere formation. For Sci Int. 154 (2005), pp. 35-43.

Gitto, L. Bonaccorso, L. Maiese, A. dell’Aquila, M. Arena, V. Bolino, G. A scream from the past: A multidisciplinary approach in a concealment of a corpse found mummified. Journal of Forensic and Legal Medicine. 32 (2015), pp. 53-58.

Kumar, T. S. M. et al. Early adipocere formation: A case report and review of literature. Journal of Forensic and Legal Medicine. 16 (2009), pp. 475-477.

Rich, J. Dead, D. E. Powers, R. H. 2005. Forensic Medicine of the Lower Extremity. Totowa, New Jersey: Humana Press Inc.