Microbial neoformation of volatiles: implications for the estimation of post-mortem interval in decomposed human remains in an indoor setting

A review of multi-disciplinary decomposition research and key drivers of variation in decay

The decomposition of animal remains is a multifaceted process, involving ecological, biological, and chemical interactions. While the complexity is acknowledged through concepts like the necrobiome, it's unclear if this complexity is reflected in research. Appreciation of the complexity of decomposition is crucial for identifying sources of variation in estimations of time since death in medico-legal science, as well as building broader ecological knowledge of the decomposition process. To gain insights into the extent of multidisciplinary research in the field of decomposition science, we conducted an examination of peer-reviewed literature on four key drivers of variation: volatile organic compounds, microbes, drugs/toxins, and insects. Among 650 articles, we identified their scientific discipline, driver/s of variation investigated, and year of publication. We found that 19% explored relationships between two drivers, while only 4% investigated interactions between three. None considered all four drivers. Over the past three decades, there has been a steady increase in decomposition research publications, signifying its growing importance. Most research (79%) was linked to forensic science, highlighting opportunities for interdisciplinary collaboration in decomposition science. Overall, our review underscores the need to incorporate multidisciplinary approaches and theory into contemporary decomposition research.

"Not everything that can be counted counts" in ethanol toxicological results: an antemortem and postmortem technical interpretation focusing on driving under the influence

Ethanol blood analysis is the most common request in forensic toxicology, and some studies point to positive results in approximately one-third of all unnatural deaths. However, distinguishing sober deaths from drunk deaths is not as simple as it may seem. This technical, clinical, and forensic interpretation is proposed to interpret the ethanol toxicological results, discussing several artefacts and pitfalls that must be considered, namely focusing on driving under the influence. This work is presented with a practical and objective approach, aiming to alleviate the complexities associated with clinical, physiological, pathophysiological, and toxicological aspects to enhance comprehension, practicality, and applicability of its content, especially to courts. Particularly the physical integrity of the body, the postmortem interval, putrefactive signs, anatomic place of blood collection, alternative samples such as vitreous humour and urine, the possibility of postmortem redistribution, the inclusion of preservatives in containers, and optimal temperature conditions of shipment are among some of the aspects to pay attention. Although several biomarkers related to postmortem microbial ethanol production have been proposed, their translation into forensic routine is slow to be implemented due to the uncertainties of their application and analytical difficulties. Specifically, in the interpretation of ethanol toxicological results, "not everything that can be counted counts and not everything that counts can be counted" (attributed to Albert Einstein).

Microbiology and postmortem interval: a systematic review

This systematic review aims to learn if and how it is possible to use the human microbiome to indicate the time elapsed after death. Articles were searched on the PubMed database using predefined data fields and keywords; reviews, systematic reviews, and meta-analyses were excluded. The final selection included 14 papers (out of 144). The results indicated that the microorganisms present in the cadaveric island succeed predictably over time, with markers between the stages of decomposition constituting a potential innovative tool for postmortem interval (PMI) estimation. The human microbiome has the potential to be used for PMI estimation and may present advantages as microbes are present in all seasons, in all habitats, including the most extreme ones, and because microbial communities respond predictably to environmental changes.

An unusual case of corpse concealment driven by emotional distress

Corpse concealment involves hiding a body for criminal purposes for many different reasons, such as destroy evidence of a murder or avoid the discovery of the victim. Although defendants could argue that they did not conceal the corpse with any criminal intent, but rather to spare themselves or others from emotional distress or to honor the wishes of the deceased. However, these arguments are often challenging to substantiate, and defendants may encounter significant legal obstacles when attempting to justify their actions. Herein, we report a case involving the concealment of a woman's corpse by her father. Autopsy and histological investigations were significantly limited due to the advanced decomposition of the body. Nevertheless, by integrating these data with radiological findings obtained from total body CT and micro-CT of the larynx-hyoid complex, hanging was deemed the cause of death. Additionally, the psychological evaluation of the father indicated that the act of concealment was motivated by emotions rather than criminal intent.

Unusual concentration of tramadol detected in cadaver in the last stage of decomposition and in fly larvae in the immediate vicinity: case report and literature review

Determination of the manner and cause of death from skeletal remains is almost always very difficult and can be a challenge for medical examiners. At the end also on skeletal remains, it is possible to assess mechanical, chemical, and thermal injuries, although it can be usually impossible. Possibilities to analyze biological material for the presence of drugs are also limited. The present study describes a case of a homeless man's skeletal remains on which a large number of fly larvae were found. Unusually high concentration of tramadol (TML) in the bone marrow (BM) = 4530 ng/g, muscle (M) = 4020 ng/g, and fly larvae (FL) = 280 ng/g was detected using a validated GC/MS method. In all analyzed samples, caffeine and N-desmethyltramadol (except BM) were qualitatively determined. Autopsy findings and toxicological analyses of the BM suggested that the cause of death could probably be intoxication by TML. It is apparent from the reviewed literature that analysis of TML in the late stages of decomposition of human body is rarely performed. Literature is predominantly focused on animal studies. Thus, TML concentrations analyzed in BM, M, or FL could be found helpful in relation to evaluation of intoxication by this substance. However, the significance of the results obtained in the presented study should be confirmed by further analyses of BM, M, or FL, where TML would be proved in lethal concentration in the blood.

A primary study of ethanol production in postmortem liver and muscle tissue of rats

OBJECTIVE

To study the characteristics of postmortem ethanol production and its relation with alcohol congeners in postmortem rat liver and muscle tissues.

METHOD

Postmortem liver and muscle tissues in Sprague-Dawley rats, from postmortem time interval (PMI) day 0-20, were analyzed via headspace gas chromatograph flame ionization detection to observe production of postmortem ethanol and 5 selected alcohol congeners.

RESULT

1. Putrid ethanol production increased gradually to a peak and then decreased with the prolongation of PMI; 2. Acetaldehyde, 1-propanol, and 3-methyl-butyraldehyde were produced along with postmortem ethanol; 1-butanol was only detected from day 11-20; 3. The concentrations of acetaldehyde, 1-propanol and 3-methyl-butyraldehyde was related with ethanol production. Fifteen mathematical models were constructed for putrid ethanol production based on acetaldehyde, 1-propanol, and 3-methyl-butyraldehyde.

CONCLUSION

A peak in postmortem ethanol production was identified. The production trends of acetaldehyde, 1-propanol, and 3-methyl-butyraldehyde in the liver, and of 1-propanol in muscle, were consistent with those of ethanol, and could potentially to be used as biomarkers of postmortem ethanol production. Further human samples and data analysis are needed to verify this.

Preanalytical factors influencing the results of ethanol analysis in postmortem specimens

Excessive drinking and drunkenness are underlying factors in many fatal accidents, which make the quantitative determination of ethanol in postmortem (PM) specimens an essential part of all unnatural death investigations. The same analytical methods are used to determine ethanol in blood taken from living and deceased persons although the interpretation of the results is more complicated in medical examiner cases owing to various preanalytical factors. The biggest problem is that under anaerobic conditions ethanol can be produced naturally in decomposed bodies by microbial activity and fermentation of blood glucose. Ways are needed to differentiate antemortem ingestion of ethanol from PM synthesis. One approach involves the determination of ethanol in alternative specimens, such as bile, cerebrospinal fluid, vitreous humor and/or urine, and comparison of results with blood alcohol concentration (BAC). Another approach involves the analysis of various alcohol biomarkers, such as ethyl glucuronide, ethyl sulfate and/or phosphatidylethanol or the urinary metabolites of serotonin 5-hydroxytryptophol/5-hydroxyindoleacetic acid (5-HTOL/5-HIAA). If ethanol had been produced in the body by microbial activity, the blood samples should also contain other low-molecular volatiles, such as acetaldehyde, n-propanol and/or n-butanol. The inclusion of 1-2% w/v sodium or potassium fluoride, as an enzyme inhibitor, in all PM specimens is essential to diminish the risk of ethanol being generated after sampling, such as during shipment and storage prior to analysis. Furthermore, much might be gained if the analytical cut-off for reporting positive BAC was raised from 0.01 to 0.02 g% when PM blood is analyzed. During putrefaction low BACs are more often produced after death than high BACs. Therefore, when the cadaver is obviously decomposed, a pragmatic approach would be to subtract 0.05 g% from the mean analytical result. Any remaining BAC is expected to give a more reliable indication of whether alcohol had been consumed before death.

Retrospective analysis of factors affecting rate of skeletonization within a tropical climate

Estimating the post mortem interval (PMI) in skeletonized cases is an extremely challenging exercise. Sri Lanka lacks adequate taphonomic research which is a serious limitation when assessing PMI in forensic death investigations. Methods that have been proposed to estimate PMI using the total body score (TBS) and accumulated degree days (ADD) are mainly based on data from continental and temperate climates and have shown less reliability in tropical climates. With the intention of developing a region-specific, evidence-based guide which would be applicable to tropical climates like Sri Lanka, we selected thirteen skeletonized remains with known PMIs from forensic case records and analysed their taphonomy in relation to selected weather data. We also compared the ADD values within our dataset with reference ranges calculated using published formula. All except one were found from outdoor locations. The TBS ranged from 24 to 32 and had a weak positive correlation with the PMI. The earliest appearance of skeletonization was 15 days in a body found indoors. The highest rate of skeletonization was seen in a body with a TBS of 32 and a PMI of 23 days. The average daily temperature and relative humidity were similar across all the cases however, the amount of rainfall varied. Bodies exposed to monsoon rains (n = 6) had a lower mean rate of skeletonization compared to those that were not exposed (n = 4) suggesting lower rates of decomposition during periods of heavy rainfall. No correlation was found between ADD and TBS. In 9 (69.2%) cases, the actual ADD was much lower than reference ADD ranges for TBS values, indicating poor applicability of TBS and ADD based formulae in estimating PMI within the Sri Lankan climate. Our study shows a strong need for taphonomic and entomological research in tropical climates to further explore the impact of monsoons on biotic and abiotic factors affecting skeletonization.

A synthesis of carcass decomposition studies conducted at a tropical (Aw) taphonomy facility: 2013-2022

Decomposition studies have been conducted in several regions of the world, but relatively few have investigated taphonomy in tropical environments. Even fewer have explored carcass decomposition during multiple tropical seasons, leaving the relationships between season and decomposition in tropical environments poorly understood. Ten decomposition studies using 30 carcasses were conducted in Honolulu, Hawaii, USA to start addressing this knowledge gap. These studies show that some postmortem processes were observed regardless of season. Carcass temperature and chemistry were spatiotemporally variable. Fly larval masses were consistently observed within 3 days (∼75 ADD) postmortem and carcasses lost 60%-90% of mass by 10 days (∼250 ADD) postmortem (Total Body Score ∼26). Season had a significant effect on decomposition, yet the warmest and most humid seasons did not always result in the most rapid and extensive decomposition. Seasonal variation appears to be less pronounced than at other tropical decomposition sites.

Development and implementation of forensic anthropology in Swedish forensic practice

This paper presents the ongoing development of forensic anthropology in Sweden. We discuss the background of the discipline, its application, as well as its current and potential development in Swedish forensic practice. Collaboration with osteoarchaeologists in skeletal forensic cases has a long tradition in Sweden. Analyses of skeletal remains are performed ad-hoc, in contrast to analyses of fleshed human remains. While several law enforcement employees are educated in forensic anthropology and/or osteoarchaeology, they are not employed in these fields, and regional variations are evident. Internationally, forensic anthropology has become an autonomous forensic discipline over the past decades, requiring skills beyond mere skeletal analysis. To keep on a par with international standards, it may be time to revisit the concept of forensic anthropology in Sweden. Despite the limited presence of supporting organisational structures and systems, forensic anthropological and hard-tissue-reliant physico-chemical analyses have proven valuable in Swedish forensic practice, especially in cases of personal identification, trauma analysis and search efforts. We argue that Sweden could benefit from making qualified forensic anthropology expertise available in all law enforcement regions, starting to implement and promote forensic anthropology in routine forensic casework and formalising the role of forensic anthropology practitioners.

Modeling microbial ethanol production by S. aureus, K. pneumoniae, and E. faecalis under aerobic/anaerobic conditions - applicability to laboratory cultures and real postmortem cases

A quite intriguing subject being intensively researched in the forensic toxicology field is the source of postmortem determined blood ethanol concentration: antemortem ingestion or postmortem microbial production. Our previous research on microbial ethanol production has reported a quantitative relationship between the ethanol and the higher alcohols and 1-butanol produced by Escherichia coli, Clostridium perfrigens, and Clostridium sporogenes. In this contribution, we continue our research reporting on the following: (i) the patterns of ethanol, higher alcohols, and 1-butanol production by the microbes Klebsiella pneumoniae, Staphylococcus aureus, and Enterococcus faecalis (all being aerobic/facultative anaerobic species, common corpse's colonizers, and ethanol producers), under controlled laboratory conditions, (ii) the mathematical modeling, with simple mathematical equations, of the correlation between ethanol concentration and the other studied alcohols' concentrations, by performing multiple linear regression analysis of the results, and (iii) the applicability of the constructed models in microbial cultures developed under different temperature than that used to build the models, in denatured blood cultures and in real postmortem cases. The aforementioned alcohols were proved to be all indicators of ethanol production, both in qualitative and quantitative terms. 1-Propanol was the most significant alcohol in modeling microbial ethanol production, followed by methyl-butanol. The K. pneumoniae's models achieved the best scoring in applicability (E < 40%) compared to the S. aureus and E. faecalis models, both at laboratory microbial cultures at 37 °C and real postmortem cases. Overall, a noteworthy accuracy in estimating the microbial ethanol in cultures and autopsy blood is achieved by the employed simple linear models.