Odour profile of human corpses: A review

Establishing the volatile organic compound profile and detection capabilities of human remain detection dogs to human bones

The detection of skeletal remains using human remain detection dogs (HRD) is often reported anecdotally by handlers to be a challenge. Limited studies have been conducted to determine the volatile organic compounds (VOCs) emitted from bones, particularly when there is limited organic matter remaining. This study aimed to determine the VOCs emitted from dry, weathered bones and examine the detection performance of HRD dogs on these bones when used as training aids. The VOCs of four different bones (clavicle, rib, humerus, and vertebrae) from three cadavers were collected using sorbent tubes and analyzed using comprehensive two-dimensional gas chromatography‒time-of-flight mass spectrometry (GC × GC‒TOFMS). Subsequently, the responses of the HRD dogs to the bone samples were recorded over two separate two-day trials. A total of 296 VOCs were detected and classified into chemical classes, with aromatics and linear aliphatics being the most abundant classes. Several differences in the chemical class distribution were observed between the bone types, but the number and intensity of the VOCs were similar between the bone samples. During the HRD dog training, a higher false detection rate was observed on the first day of each trial; however, the detection rate improved to 100 % on the second day of each trial. Although the dogs are capable of detecting bones, they require exposure to and training with a diverse range of skeletal remains to enhance their efficiency. This is necessary due to the variations in the types and intensity of VOCs compared to earlier decomposition stages involving soft tissue.

Ancient Egyptian Mummified Bodies: Cross-Disciplinary Analysis of Their Smell

Ancient Egyptian mummification was a mortuary practice aimed at preserving the body and soul for the afterlife, achieved through a detailed ritual of embalming using oils, waxes, and balms. While most research on Egyptian mummified bodies has so far been conducted in European collections, our study focuses on the collection of the Egyptian Museum in Cairo. The goal was to evaluate whether contemporary smells reflect the mummification materials and, if so, what information can be of value to collection interpretation and conservation. We combined panel-based sensory analyses with gas chromatography-mass spectrometry-olfactometry (GC-MS-O), microbiological analysis, and historical and conservation research. Apart from differences in odor intensity, the sensory analyses highlighted common olfactory descriptors for all samples: "woody", "spicy", and "sweet". GC-MS-O identified four categories of volatiles based on their origin: (i) original mummification materials; (ii) plant oils used for conservation; (iii) synthetic pesticides; and (iv) microbiological deterioration products. However, the use of insect repellents similar in composition to the original mummification materials makes it challenging to attribute the origin of some compounds. Clusters based on the chemical and olfactory profiles of the smells emerged, suggesting similarities based on the archeological period, conservation treatments, and materiality.

From carrion to soil: microbial recycling of animal carcasses

Decomposer microbial communities are gatekeepers in the redistribution of carbon and nutrients from dead animals (carrion) to terrestrial ecosystems. The flush of decomposition products from a carcass creates a hot spot of microbial activity in the soil below, and the animal's microbiome is released into the environment, mixing with soil communities. Changes in soil physicochemistry, especially reduced oxygen, temporarily constrain microbial nutrient cycling, and influence the timing of these processes and the fate of carrion resources. Carcass-related factors, such as mass, tissue composition, or even microbiome composition may also influence the functional assembly and succession of decomposer communities. Understanding these local scale microbially mediated processes is important for predicting consequences of carrion decomposition beyond the hot spot and hot moment.

Soil elemental changes during human decomposition

Mammalian decomposition provides pulses of organic matter to the local ecosystem creating ephemeral hotspots of nutrient cycling. While changes to soil biogeochemistry in these hotspots have been described for C and N, patterns associated with deposition and cycling of other elements have not received the same attention. The goal of our study was to evaluate temporal changes to a broad suite of dissolved elements in soils impacted by human decomposition on the soil surface including: 1) abundant mineral elements in the human body (K, Na, S, P, Ca, and Mg), 2) trace elements in the human body (Fe, Mn, Se, Zn, Cu, Co, and B), and 3) Al which is transient in the human body but common in soils. We performed a four-month human decomposition trial at the University of Tennessee Anthropology Research Facility and quantified elemental concentrations dissolved in the soil solution, targeting the mobile and bioavailable fraction. We identified three groups of elements based on their temporal patterns. Group 1 elements appeared to be cadaver-derived (Na, K, P, S) and their persistence in soil varied based upon soluble organic forms (P), the dynamics of the soil exchange complex (Na, K), and gradual releases attributable to microbial degradation (S). Group 2 elements (Ca, Mg, Mn, Se, B) included three elements that have greater concentrations in soil than would be expected based on cadaver inputs alone, suggesting that these elements partially originate from the soil exchange (Ca, Mg), or are solubilized as a result of soil acidification (Mn). Group 3 elements (Fe, Cu, Zn, Co, Al) increased late in the decomposition process, suggesting a gradual solubilization from soil minerals under acidic pH conditions. This work presents a detailed longitudinal characterization of changes in dissolved soil elements during human decomposition furthering our understanding of elemental deposition and cycling in these environments.

Copycatting the smell of death: Deciphering the role of cadaveric scent components used by detection dogs to locate human remains

Human remains detection dogs (HRDD) are commonly used by law enforcement agencies to search for cadavers. Biological material is typically used as a training stimulus, also called aids, to train dogs to recognize the smell of cadavers. While HRDD training approaches have received extensive attention, information remains limited on the olfactory cues used to train them. Here, we aimed to decipher the chemical basis of detection dog olfaction. Five specific objectives were explored to precise whether the composition or the concentration of the training aids drives the HRDDs responses. We recorded the behavioral responses of four HRDDs exposed to different cadaveric-like smells. We found that HRDDs recognized a simplified synthetic aid composed of cadaveric compounds. The lowest concentration at which HRDDs continued to perceive the cadaveric smell was determined. HRDDs were not impacted by slight modifications to the chemical composition of a blend of odors that they have been trained with. HRDDs associated sulfur and nitrogen compounds as human cadaver. Our findings highlight a lack of specificity of HRDDs to cadaveric compounds, which could lead to error of detection. Moreover, all dogs did not positively respond to the same blends, despite being trained with the same aids and procedure. However, we confirmed that dogs could be trained with a simplified blend of molecules. The chemical composition of a training aid has, therefore, high consequences on the performance of the trained animal, and this conclusion opens additional questions regarding olfaction-based detection animals.

Cadaver Dogs and the Deathly Hallows-A Survey and Literature Review on Selection and Training Procedure

Human remains detection dogs (HRDDs) are powerful police assets to locate a corpse. However, the methods used to select and train them are as diverse as the number of countries with such a canine brigade. First, a survey sent to human remains searching brigades (Ncountries = 10; NBrigades = 16; NHandlers = 50; Nquestions = 9), to collect their working habits confirmed the lack of optimized selection and training procedures. Second, a literature review was performed in order to outline the strengths and shortcomings of HRDDs training. A comparison between the scientific knowledge and the common practices used by HRDDs brigade was then conducted focusing on HRDDs selection and training procedures. We highlighted that HRDD handlers select their dogs by focusing on behavioral traits while neglecting anatomical features, which have been shown to be important. Most HRDD handlers reported to use a reward-based training, which is in accordance with training literature for dogs. Training aids should be representative of the odor target to allow a dog to reach optimal performances. The survey highlighted the wide diversity of homemade training aids, and the need to optimize their composition. In the present document, key research topics to improve HRDD works are also provided.

Behavioral and Electrophysiological Responses of the Fringed Larder Beetle Dermestes frischii to the Smell of a Cadaver at Different Decomposition Stages

A cadaver is colonized by a wide diversity of necrophagous insects. It is well documented that Dipterans are attracted by the volatile organic compounds (VOCs) released by a corpse during the first minutes following death. Coleopterans are known to be attracted by highly decomposed cadavers, but have received less attention regarding the olfaction-based mechanisms underlying these interactions. In the present study, we impregnated gauzes with VOCs collected from each decomposition stage of dead rats: fresh, bloated, active, and advanced decay. We collected the VOCs released by the gauze and confirmed what was previously know from the literature: the decomposition stages are associated with contrasting chemical profiles. We exposed Dermestes frischii Kugelann (Coleoptera: Dermestidae) male and female antennae to the same gauzes and found that stronger electrical responses were recorded when using the smell of the advanced decay stage. Finally, we performed two choices behavioral assays. Females showed no preference for the four decomposition stages, while males were attracted by the smell associated with active and advanced decay stages. These results suggest that specific VOCs released by a decaying body guide necrophagous coleopterans to their feeding site. Whether D. frischii males release pheromones to attract females remains to be tested.