Postmortem Electrical Conductivity Changes of Dicentrarchus labrax Skeletal Muscle: Root Mean Square (RMS) Parameter in Estimating Time since Death

Electric impedance spectroscopy techniques have been widely employed to study basic biological processes, and recently explored to estimate postmortem interval (PMI). However, the most-relevant parameter to approximate PMI has not been recognized so far. This study investigated electrical conductivity changes in muscle of 18 sea bass specimens, maintained at different room temperatures (15.0◦C; 20.0◦C; 25.0◦C), during a 24 h postmortem period using an oscilloscope coupled with a signal generator, as innovative technology. The root mean square (RMS) was selected among all measured parameters, and recorded every 15 min for 24 h after death. The RMS(t) time series for each animal were collected and statistically analyzed using MATLAB®. A similar trend in RMS values was observed in all animals over the 24 h study period. After a short period, during which the RMS signal decreased, an increasing trend of the signal was recorded for all fish until it reached a peak. Subsequently, the RMS value gradually decreased over time. A strong linear correlation was observed among the time series, confirming that the above time-behaviour holds for all animals. The time at which maximum value is reached strongly depended on the room temperature during the experiments, ranging from 6 h in fish kept at 25.0◦C to 14 h in animals kept at 15.0◦C. The use of the oscilloscope has proven to be a promising technology in the study of electrical muscle properties during the early postmortem interval, with the advantage of being a fast, non-destructive, and inexpensive method, although more studies will be needed to validate this technology before moving to real-time field investigations

Evaluation of decay odor as a time since death indicator

Until recently, decay odor has not been used as a forensic investigative tool beyond body reconnaissance by cadaver dogs. The research presented in this study is attempting to broaden the value of decay odor through evaluating it as a time since death indicator. Decomposition is the result of two internal processes, autolysis and putrefaction, and many external factors, i.e., bacteria, carnivores, insects. Autolysis is the breakdown to cells following circulatory stasis. Putrefaction is the destruction of the organism through bacterial activity. Some of the byproducts of putrefaction are odiferous compound such as cadaverine, putrescine, volatile fatty acids (VFA\u27s), methane and hydrogen sulfide, which produce the decay odor. As decomposition progresses the concentration of various by-products that contribute to the decay odor are expected to vary in a predictable pattern that correlates to temperature. To test this hypothesis the odors of several decaying corpses were collected and analyzed using electronic nose technology. The greatest obstacle to successfully studying decay odor was the collection of a representative and replicable sample. A portable sampling device was designed to collect an appropriate sample. The device consisted of connecting three glass pipettes filled with molecular sieve to the inflow nozzle of an air pump. Molecular sieve, a universal dryant, was capable of capturing the odor causing agents under field conditions and releasing the same agents under the analytical conditions of the electronic nose in the laboratory. Collecting three samples simultaneously, per the three pipettes, minimized the intersample error and reduced the sampling time. Aroma samples were collected from eleven decaying individuals at regular intervals. The human subjects were donated for scientific study and met several criteria: 1) known time of death, 2) known cause of death, 3) received during the fresh stage of decomposition, and 4) unautopsied. Included in the study were eight males and three females. All individuals were white, non-Hispanic. Age range was from 25 to 98 years. Cause of death was natural in all case but three, two suspected drug overdose and one suicide by hanging. Ten corpses were enclosed in a body bag during the decomposition process to concentrate and isolate the odor. One corpse was not placed in a body bag. A small hole was cut in each body bag through which the sample was taken. At each sampling event the temperature and humidity, as well as the intersample high and low temperature and humidity and rainfall, were recorded. The fluctuation and accumulated effects of temperature was summarized as accumulated degree days (ADD). Control samples were collected by sampling air contained within empty body bags. Four of the ten body bags were disturbed by carnivore activity during the decay process. The results of the study show that the aroma pattern as detected by the electronic nose did not change over time. However, the concentration of the odor did change. The intensity of the odor positively correlated to ADD when the body was isolated in an undisturbed body bag. Intensity of the odor did not correlate to ADD when the body bag was disturbed or the body was not placed in a body bag. At this time, odor as a time since death indicator is only applicable to a sample collected from bodies isolated in body bags. In order to expand the applicability of this method the sensitivity of the sampling method must be improved. Furthermore, important odor pattern variation may become detectable with increased sensor sensitivity of the electronic nose. In sum, the concentration of odor positively correlated to ADD when specific conditions are met. However, aroma pattern change is undetectable

Nutrient dynamics of annual ryegrass as a tool in forensic investigation on burial sites

The burial of a corpse presents forensic investigators with the problems of gravesite location and post deposition estimation. Botany has a predominant role in the assessment of graves, its potential for providing temporal and gravesite indication is continually being researched. This research aimed to provide a proof of concept of the use of Dumas combustion on ryegrass growing on decomposing pork, and provide temporal and grave indication. The experimental design, involved growing tetraploid ryegrass seeds over two different growing mediums; washed river sand and ground soil. Grass was left to grow within the growing mediums which consisted of repetitions of buried pork, non-fertiliser treated and non-pork treated groups. Grass was harvested, dried and underwent nitrogen and ICP analysis. The dry matter yield of grass that resulted, show some level of growth difference between grass grow on buried pork and non-treated control groups. Nitrogen levels between these groups was also very different with increased levels seen between all groups on the second harvest, non-fertiliser treated groups were an exception. Further research is warranted to explore the full use of Dumas and validate the observations noted

Investigating the Potential of Postmortem Metabolomics in Mammalian Decomposition Studies in Outdoor Settings

By focusing on solely forensic studies, this dissertation gives an overview of three seemingly independent studies, which at a deeper level, reveal their strong interconnectivity through their forensic importance. The consistent global theme carried through all chapters circles around the application of metabolomics on biological specimens collected postmortem at an outdoor taphonomy facility in Knoxville, Tennessee, USA. The overall intention was to fill the knowledge gap around postmortem metabolomics while stressing its importance in bridging analytical chemistry and forensic science. Global postmortem metabolomics studies will contribute to the so-far conducted taphonomic groundwork by providing a better understanding of the fundamental processes of decomposition and ultimately build a more comprehensive postmortem biochemical database. The first chapter applies postmortem metabolomics to soils and human skeletal remains obtained from a multi-individual grave. The primary goals of this study were: (1) to obtain insights into the metabolite pulse released from buried remains into grave soils at different depths of a shallow burial and (2) to assess metabolic signatures of bones using an inter- and intraindividual analysis approach. Decomposition progresses differently below ground compared to the soil surface with impacts on rates and patterns of decomposition. In contrast to the first chapter, the second chapter faces an environmental change with a study design constructed around surface decomposition. Additionally, given that rates and patterns of decay seem to vary among species, a comprehensive omics approach including metabolomics and lipidomics was utilized to investigate species-specific metabolic signatures in soils from the cadaver decomposition island. The final chapter completes the aforementioned studies by investigating one of the most complex of all factors – intrinsic drivers of decomposition. We evaluated the trackability of drugs through several specimens such as serum, larvae, decomposition fluid, and soils from human donors. Furthermore, comprehensive postmortem metabolomics of the same specimens provided (a) matrix-specific metabolic signatures, (b) groups of metabolites potentially useful as decomposition biomarkers, and (c) an assessment of possible impacts of perimortem health conditions on the postmortem metabolome

Spatial Geochemical Changes in Central and East Texas Soils over Time Resulting from Human Decomposition

Human decomposition is studied to aid forensic investigations and better understand the impact of cemeteries on urban resources like soil and groundwater. The purpose of this study was to identify changes in soil geochemistry at and around a human grave to search for lateral nutrient movement and possibly identify new patterns in elemental concentrations that could be used in estimating post-mortem intervals (PMIs). At the Forensic Anthropology Research Facility (FARF) at Texas State San Marcos, soil samples were collected from a shallow grave over the course of 54 days to conduct analysis for organic matter content, texture, pH, and bulk elemental concentrations in native central Texas soils. East Texas soils were also brought in and placed underneath the body for comparative analysis. Organic matter content sharply increased at the beginning of the observation period before steadily declining, while pH showed the opposite trend. There was an initial decrease in pH, followed by significant increases under and around the body towards the end of the study. At a 25 cm distance from the body, there were significant changes in the soil content of Fe, Ca, and Al, with trends for Fe and Al over time both under and around the body showing promise as a potential chemical marker to aid in estimating PMI. This indicates a lateral migration of nutrients in the soil, likely as a result of bioturbation in the soil by microfauna. Further study of these indicators, especially on uncovered and more deeply buried bodies, could provide the more robust statistics necessary to consider Fe and Al concentrations in the soil when estimating how long a decomposing body may have been present. Investigation of more chemical indicators may be crucial in the future of missing and murdered persons cases, and it informs the body of knowledge relating to effects of cemeteries on the environment and nearby populations

The Development and Evaluation of Impedance Technology to Determine the Quality of Shrimp and Catfish.

Impedance technology is currently used as a measurement of microbial activity. The purpose of the current study was to determine the feasibility of utilizing impedance technology to evaluate the quality of white shrimp (marine species) and channel catfish (freshwater species). Impedance analysis measurements (I-values) of raw shrimp increased for samples stored at 5, 25, and 35\sp\circC; however, control samples stored at $-$20\sp\circC displayed no significant changes in I-values. I-values from thermally processed shrimp had no direct relationship with odor scores, increased storage time, or increased storage temperature. It was concluded that while impedance measurements were able to indicate the degree of raw shrimp quality, they were ineffective for determining the quality of cooked shrimp. Methods currently utilized in this study to determine quality include degradation product measurement, odor analysis, psychrotrophic bacterial enumeration, and pH. Comparisons of raw shrimp I-values and odor scores demonstrated a strong relationship, particularly with increased storage time and temperature. Impedance analysis of channel catfish demonstrated no relationship with other quality indicators. Measurements of the nucleoside inosine correlated highly with odor scores, which demonstrated that inosine quantification has the potential for use as an indicator of catfish quality. The effect of rigor mortis on impedance measurements was also examined in this study. While rigor mortis occurred in catfish muscle within the first 5 hours postmortem, no relationship was established with impedance. This study demonstrated that impedance can measure shrimp quality, but not catfish quality, and that the nucleoside inosine could be a potential indicator of catfish quality

Insect olfaction as an information filter for chemo-analytical applications

Die Geruchswahrnehmung von Insekten ist an die spezifischen Anforderungen der Ökosysteme angepasst, in denen sie leben. Von Insekten wahrgenommene Volatile können Informationen über den Ort eines geeigneten Ovipositionsplatzes oder den physiologischen Zustand einer Wirtspflanze geben. Da der Geruchssinn der Insekten sich seit Millionen von Jahren an die Wahrnehmung bestimmter Volatile angepasst hat, können die wahrgenommenen Volatile als Markerstoffe angesehen werden, die zuverlässig einen Ökosystemzustand angeben können. Die Identifikation dieser Markerzustände und die Evaluation ihrer Nützlichkeit für spurenanalytische Anwendungen ist das Ziel dieser Arbeit. Es wurden drei Themen ausgewählt um die Verwendungsmöglichkeit des Insektengeruchssinns für Sensoranwendungen zu überprüfen: Fleischfrische, Todeszeitbestimmung (post mortem Intervall, PMI) und frühzeitige Feuererkennung. Spurenanalytik (GC-MS), Elektrophysiologie (EAG, GC-MS/EAD), Verhaltensversuche und Feldtests wurden angewandt, um die chemoökologische Interaktion der Schmeißfliege Calliphora vicina und der „Feuerkäfer“ Melanophila cuspidata, Merimna atrata and Acanthocnemus nigricans mit ihrer natürlichen Umgebung zu untersuchen. Die Resultate aus diesen Methoden erlaubten die Selektion von Volatilen, die drei Kriteria erfüllen: hohe Quantität, zuverlässige Emission und die ausschliessliche Emission von der untersuchten und keiner anderen Quelle. Diese drei Auswahlkriterien wurden aufgestellt um zu gewährleisten, dass die ausgewählten Markervolatile nicht nur zuverlässig mit dem physiologischen Status der Substrate (Alter von verderbendem Fleisch, PMI, Temperatur von erhitzten Spänen) korrelieren, sondern auch den Ansprüchen technischen Sensorsysteme genügen. Im Falle des alternden Fleisches unter warmen und trockenen Bedingungen ist Nonanal ein Zeiger für die korrekte Reifung des Fleisches zu Schinken. Dimethyl Trisulfid, Phenol und Indol zeigen das Verderben des Fleisches unter warmen und feuchten Bedingungen an. Bei niedrigen Temperaturen sind zunehmende 2,3 Butandiol Emission und abnehmende Nonanal Emission ein Zeiger für zunehmendes Verderben des Fleisches, sowohl unter trockenen als auch feuchten Bedingungen. Allerdings wurde 2,3 Butandiol nicht von C. vicina wahrgenommen, da die Fliege während der Vegetationszeit aktiv ist und unter diesen Bedingungen Dimethyl Trisulfid, Phenol und Indol emittiert werden. Nonanal, Hexanal, Dimethyl Disulfid, Dimethyl Trisulfid, Butan-1-ol und Phenol wurden als nützliche Volatile zur Eingrenzung der Leichenliegezeit ausgewählt. Die genannten Aldehyde sind typisch für die frühen Stadien der Verwesung, gefolgt von Butan-1-ol und den Schwefelsulfiden. Phenol wird hauptsächlich in den späteren Verwesungsstadien emittiert. Allerdings werden Phenol und 1-Butanol nicht von der Fliege wahrgenommen, da diese ein Generalist ist und nicht zwischen dem geblähten und aktivem Stadium der Verwesung unterscheiden muss. Daher wird zusätzlich die Geruchswahrnehmung des Speckkäfers Dermestes maculans betrachtet. Die Untersuchung anderer necrophager Insekten können weitere Einblicke in die Zeitabhängigkeit der Volatilemissionen während der Vertebratenverwesung geben. Die im Rahmen dieser Arbeit gewonnenen Ergebnisse erlauben eine Korrelation zwischen Emissionen und Leichenliegezeit und können eine Grundlage für eine volatilenbasierte post mortem Zeitbestimmung für Polizeikräfte sein. Terpene, aliphatische Aldehyde, Furfural und Methoxyphenole werden von erhitztem Holz emittiert. Komponenten aus all diesen Stoffklassen werden von M. cuspidata und M. atrata wahrgenommen, da diese Käfer den Erhitzungszustand von Baumstämmen nach einem Feuer erkennen können, um einen geeigneten Ovipositionsplatz zu finden. A. nigricans nimmt vor allem Methoxyphenole wahr, wohingegen M. atrata und M. acuminata Furfural zur Orientierung verwenden. Diese Unterschiede komplementieren das bekannte Verhalten dieser Käfer in ihrer natürlichen Umgebung, da A. nigricans auf verkohlten Stämmen, die große Mengen von Methoxyphenolen emittieren, seine Eier ablegt, und M. atrata und M. cuspidata auf Stämmen ihre Eier ablegen, die vom Feuer zwar äußerlich verkohlt, aber innerlich nur erhitzt wurden und daher Furfural emittieren. Halbleitergassensoren, die Furfural mit einer ausreichenden Selektivität vermessen können, können Holzbrände schon während ansteigender Temperatur und damit vor der Entzündung detektieren. Derartige Sensoren können sowohl als neuartige Frühwarnsysteme für die holzverarbeitende Industrie als auch für Waldbrandwarnsysteme oder den Haushalt dienen