The formation of early stage adipocere in submerged remains: a preliminary experimental study

In some circumstances, the presence of adipocere may retard decomposition and complicate postmortem interval estimation. This article explores the correlation between Accumulated Degree Days (ADD) and early stage formation of adipocere. Sixty wild rabbit (Oryctolagus cuniculus) carcasses were used in this experiment; a control group (N = 30) deposited directly on the ground surface and an experimental group (N = 30) completely submersed in water in individual buckets. Data (water and inner body temperature, pH, and total body score) were collected every 100 ADD. Results indicated that early stage adipocere is correlated to ADD and that its formation on submersed remains is more likely to occur after 630 ADD. Skin sloughing promoted the formation of adipocere. No adipocere was formed on any of the control group rabbits. This study also highlights the fact that multiple factors influence adipocere formation and it is suggested that further research needs to be conducted into this area.     

Caddisflies assist with homicide case: determining a postmortem submersion interval using aquatic insects

Although few indicators of time since death for corpses found in aquatic ecosystems are comparable in precision to the insect indicators used in terrestrial cases, there are observations that can be useful in suggesting or ruling out an approximate PMSI (postmortem submersion interval). For example, the time intervals required for certain growth phases of aquatic insects, such as caddisflies, that may attach themselves to the submerged remains can be used to estimate a minimum PMSI. Approximately 8 of the 13 orders of insects containing species with aquatic or semi-aquatic stages are likely to be associated with carrion or corpses in aquatic habitats. We present a case study in which portions of a body from an adult male were discovered in a south central Michigan stream. The body was dismembered and portions were recovered from two bags floating and submerged in the stream. Insect specimens collected from mesh and plastic bags consisted of one fly larva belonging to the family Muscidae, and caddisfly larvae belonging to two families: the Limnephilidae. (case-makers) and the Hydropsychidae, (net spinners). We used unique case-building behaviors of the limnephilid caddisflies found on the remains to elucidate a PMSI range consistent with the disappearance of the victim. It is important for forensic investigators to understand that although some precision is lost in estimating a PMSI with aquatic insects, these organisms should not be ignored in gathering evidence from aquatic crime scenes, and in fact, they can provide valuable details in estimating a PMSI.     

Rodents as taphonomic agents: bone gnawing by brown rats and gray squirrels

Passive infrared technology was used to film diurnal and nocturnal scavenging behavior of brown rats and gray squirrels at the University of Tennessee's Anthropological Research Facility. This direct documentation demonstrated that brown rats modified fat-laden cancellous bone while gray squirrels generally gnawed the thicker bone cortices only after fats had leached away. A case study placed in a shaded portion of the Facility indicated the postmortem interval for initial gnawing by gray squirrels was slightly over 30 months. An examination of 53 human skeletons in the William M. Bass Forensic Skeletal Collection revealed that 10 cases had gnaw marks consistent with those made by gray squirrels. One of the 10 cases had been gnawed within 16 months of time-since-death, while the remaining nine had postmortem intervals >30 months. Additional observed modifications made to nonhuman bone by gray squirrels indicate that squirrel gnaw marks on bone can serve as a minimal estimate of time-since-death in a temperate environment similar to that of East Tennessee.     

The potential to determine a postmortem submersion interval based on algal/diatom diversity on decomposing mammalian carcasses in brackish ponds in Delaware

Recently botanical evidence has been studied to determine if it is useful in forensic investigations. This study was performed to examine stillborn piglet decomposition in a brackish water environment and to semi-quantitatively document stages of decomposition, degree day accumulation per stage as well as the algal/diatom diversity useful in determining a postmortem submersion interval (PMSI). Piglets and ceramic tiles were submerged in brackish ponds and sampled on a regular basis to document algal diversity and succession between substrates and stages of decomposition. Significantly greater weight was lost from piglet carcasses during the early floating and advanced floating decay stages. Seasonal effects were observed in degree-day accumulations. Diatom diversity was significantly greater on piglet carcasses compared to tile substrates. Algal diversity decreased over time on the piglet carcasses as well as the stage of decomposition. A significant relationship and strong correlation between algal diversity found on the piglet substrate with time was observed. Our results indicate that more research is needed to examine the potential to use diatoms in not only determining manner of death but also the duration of time (PMSI) a victim may have been immersed in an aquatic environment.     

Taphonomic Effects of Vulture Scavenging*

Abstract: From July through September 2007, three pig carcasses (Sus scrofa), weighing between 27 and 63 kg were placed outside in a grassy area in central Texas. A surrounding fence prevented entrance by terrestrial scavengers, while allowing avian scavengers unrestricted access. A fourth pig carcass served as a control for the rate of decomposition and was placed in a cage that prevented terrestrial and avian animal access. Modification of the carcasses was recorded through the use of two motion‐sensing digital cameras and daily on‐site observations. American black vultures (Coragyps atratus) and turkey vultures (Cathartes aura) waited c. 24 h before beginning to scavenge and completely skeletonized the carcasses in 3 to 27 h of feeding, leaving scratches on the bones. The accelerated rate of decomposition and the signature markings on the bones should be considered when interpreting taphonomic events and determining an accurate postmortem interval at vulture‐modified scenes.     

不同环境条件下大鼠死后皮肤大体和组织学改变

目的研究观察大鼠在不同环境条件下死后不同时间其皮肤大体、组织学的改变,为推测较长的死后间隔时间建立实验动物依据。方法观察雌性SD大鼠在不同环境条件下的死后变化,并间隔一定死后时间取皮、染色和镜下观察。结果死后发生骨、软组织分离,A组约需35d,B组需13d。皮肤有形细胞成分和附属器完全分解破坏,A组约20d,B组7d。胶原纤维在A组死后40d（B组12d）仍有部分保留完整。结论环境温度差异是造成A、B两组发生死后改变时程不同的主要因素,利用皮肤大体、组织学改变可望较系统和准确的推测晚期死亡时间。     

Differential decomposition patterns in charred versus un-charred remains

Although researchers have examined many aspects of fire modification, the rate and pattern of decomposition in charred remains have not been studied previously. This study utilized 48 domestic pigs, divided into 24 charred (head, neck, and limbs burned to Crow-Glassman level 1 and torso to level 2) and 24 un-charred pig carcasses. Decomposition of control carcasses was scored at 50 accumulated degree days (ADD) intervals, and charred carcasses were also observed and photographed at this time. A Charred Body Scale was subsequently created, and charred carcasses were scored retrospectively for the same ADD intervals. Analysis using a mixed-effect repeated measures model indicated that, while decomposition rate was not statistically different between the two groups (p = 0.2692), the charred remains initially displayed an ostensibly more advanced pattern. Body regions displaying significant charring decomposed at a faster rate (p < 0.001), while areas with very light levels of charring decomposed at a significantly slower rate (p < 0.001).     

256例命案尸体死亡时间推断的回顾性分析

目的探讨降低死亡时间推断误差的方法。方法收集常州市和南京市2003年1月一2013年1月256例已破命案．采用传统方法进行死亡时间推断,与破案后获得的实际死亡时间进行比较,并根据死亡时间进行分组,计算死亡时间推断准确率,分析判断错误原因。结果早期尸体死亡时间（≤12h和13～24h）推断准确率分别为90％、89％,晚期尸体死亡时间（1—7d、1～2周、3～4周、1～6个月、7～12个月和1～5年）的推断准确率随时间的延长下降,分别为79％、76％、83％、79％、60％和50％。推断方法不当、水中尸体、极端温度、客观依据不足、抛尸以及变动或破坏现场是影响死亡时间推断准确率的常见因素。结论综合参考多项指标可降低死亡时间推断的误差。     

Volatile Organic Compound Profiling from Postmortem Microbes using Gas Chromatography–Mass Spectrometry

Volatile organic compounds (VOCs) are by-products of cadaveric decomposition and are responsible for the odor associated with decomposing remains. The direct link between VOC production and individual postmortem microbes has not been well characterized experimentally. The purpose of this study was to profile VOCs released from three postmortem bacterial isolates (Bacillus subtilis, Ignatzschineria indica, I. ureiclastica) using solid-phase microextraction arrow (SPME Arrow) and gas chromatography–mass spectrometry (GC-MS). Species were inoculated in headspace vials on Standard Nutrient Agar and monitored over 5 days at 24°C. Each species exhibited a different VOC profile that included common decomposition VOCs. VOCs exhibited upward or downward temporal trends over time. Ignatzschineria indica produced a large amount of dimethyldisulfide. Other compounds of interest included alcohols, aldehydes, aromatics, and ketones. This provides foundational data to link decomposition odor with specific postmortem microbes to improve understanding of underlying mechanisms for decomposition VOC production.