Dynamics of insects, microorganisms and muscle mRNA on pig carcasses and their significances in estimating PMI

Catch me if you can-emission patterns of human bodies in relation to postmortem changes

The present study examines for the first time the emission patterns and olfactory signatures of 9 complete human corpses of different stages of decomposition. Air sampling was performed inside the body bags with solid sorbents and analysed by coupled gas chromatography-mass spectrometry after thermal desorption (TD-GC-MS). Furthermore, odour-related substances were detected by gas chromatography-olfactometry (GC-O). Sulfurous compounds (mainly dimethyl di- and trisulfide) were identified as most important to the odour perception. Around 350 individual organic substances were detected by TD-GC-MS, notably sulfurous and nitrogenous substances as well as branched alkanes, aldehydes, ketones, alcohols, carboxylic acids, carboxylic acid esters and ethers. A range of terpenes was detected for the first time in a characteristic emission pattern over all decomposition stages. Concentrations of the substances varied greatly, and no correlation between the emission patterns, the stage of decomposition and the cause of death could be found. While previous studies often analysed pig cadavers or only parts of human tissue, the present study shows the importance of analysing complete human corpses over a range of decomposition stages. Moreover, it is shown that using body bags as a kind of "emission test chamber" is a very promising approach, also because it is a realistic application considering the usual transport and store of a body before autopsy.

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.

Succession patterns of sarcosaprophagous insects on pig carcasses in different months in Yangtze River Delta, China

The Yangtze River Delta is one of the most economically developed regions in China, and many cases in the area require an estimation of the postmortem interval each year. This article reports forensic entomological research conducted in this region in different months. A total of 18 domestic pigs were used to study carcass decomposition, species composition, development events, and succession patterns of insects in different months from 2015 to 2021. A total of 53 arthropod species were identified, of which 38, 40, 41, and 25 were observed in April, June, September, and November, respectively. We demonstrated that insects vary in number and species from month to month, and the same species vary in number among the different months. Larvae of Calliphoridae mainly drove the decomposition of carcasses, and the decomposition rate of carcasses varied over the months. Particularly, the decomposition rate was highest in June and September, slower in April, and slowest in November. The predominant species on the carcasses also varied from month to month; Calliphora grahami Aldrich, Chrysomya pinguis (Walker), Lucilia sericata (Meigen) (Diptera: Calliphoridae), and Hydrotaea spinigera Stein (Diptera: Muscidae) were most predominant in April; Chrysomya megacephala (F.) and Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) were most predominant in June and September; and Ca. grahami was most predominant in November. In addition, the seven dominant insect species displayed four developmental events, which could be used to determine minimum postmortem interval, including adult arrival (T1), larvae wandering (T2), pupation (T3), and eclosion (T4) time on the carcasses. Insect succession patterns on carcasses also varied across months. For example, Ch. megacephala appeared later in the composition stages and was not numerically dominant in April but appeared earlier and was dominant in June and September. The results of this study guide the use of insect evidence in different months in the Yangtze River Delta region of China for estimating the postmortem interval of carcasses.