Postfeeding Larval Dispersal Behavior of Late Season Blow Flies (Calliphoridae) in Southern Ontario,Canada

Postfeeding dispersal involves migration of larvae away from their food source in order to pupate. Puparia are difficult to find, yet are important for estimating PMI, and missing puparia during collection can result in inaccurate estimations. This study investigates the late season maggot dispersal patterns for blow flies at coyote carcasses in two habitats with an aim to improving puparia collection procedures. Puparia samples collected from various dispersal distances and directions tested the spatial distribution patterns of the various species using the variance/mean ratio (VMR). Lucilia illustris was the most common species to emerge, with a preferred minimum dispersal distance of more than 50.8 cm and an overall VMR value of 14.91, indicating this species had a clumped distribution pattern. These findings highlight that current collection procedures that use random sampling from under carcasses do not adequately account for the spatial distribution of larvae.     

Potential Use of Bacterial Community Succession in Decaying Human Bone for Estimating Postmortem Interval,,

Bacteria are taphonomic agents of human decomposition, potentially useful for estimating postmortem interval (PMI) in late‐stage decomposition. Bone samples from 12 individuals and three soil samples were analyzed to assess the effects of decomposition and advancing time on bacterial communities. Results indicated that partially skeletonized remains maintained a presence of bacteria associated with the human gut, whereas bacterial composition of dry skeletal remains maintained a community profile similar to soil communities. Variation in the UniFrac distances was significantly greater between groups than within groups (p < 0.001) for the unweighted metric and not the weighted metric. The members of the bacterial communities were more similar within than between decomposition stages. The oligotrophic environment of bone relative to soft tissue and the physical protection of organic substrates may preclude bacterial blooms during the first years of skeletonization. Therefore, community membership (unweighted) may be better for estimating PMI from skeletonized remains than community structure (weighted).     

Variation in Developmental Time for Geographically Distinct Populations of the Common Green Bottle Fly,Lucilia sericata (Meigen)*

Abstract: Time between death and discovery of remains, or postmortem interval (PMI), can be assessed using blow fly maggot age. Forensic entomologists rely on published, often nonlocal, species‐specific developmental tables to determine maggot age. In a series of common garden experiments, we investigated the developmental rate variation between populations of Lucilia sericata collected from Sacramento, CA, San Diego, CA, and Easton, MA at 16°C, 26°C, and 36°C. For the 16°C trial the time measurement started at egg hatch, while for the higher temperatures the experiment began at oviposition; the wandering stage signified the endpoint for all experiments. The distribution of developmental times differed significantly (ANOVA, p < 0.001) between the three populations within each temperature treatment. We discovered that regional variation of developmental times within a blow fly species exists. This study demonstrates the importance of assembling local population‐specific developmental tables when estimating larval age to determine PMI.     

A Longitudinal Study on Human Outdoor Decomposition in Central Texas

The development of a methodology that estimates the postmortem interval (PMI) from stages of decomposition is a goal for which forensic practitioners strive. A proposed equation (Megyesi et al. 2005) that utilizes total body score (TBS) and accumulated degree days (ADD) was tested using longitudinal data collected from human remains donated to the Forensic Anthropology Research Facility (FARF) at Texas State University‐San Marcos. Exact binomial tests examined the rate of the equation to successfully predict ADD. Statistically significant differences were found between ADD estimated by the equation and the observed value for decomposition stage. Differences remained significant after carnivore scavenged donations were removed from analysis. Low success rates for the equation to predict ADD from TBS and the wide standard errors demonstrate the need to re‐evaluate the use of this equation and methodology for PMI estimation in different environments; rather, multivariate methods and equations should be derived that are environmentally specific.     

大鼠死后肌肉总腺苷酸及腺苷酸能荷的时序性变化

目的 测定大鼠死后不同时间双后肢肌肉嘌呤腺苷酸[三磷酸腺苷(adenosine triphosphate,ATP)、二磷酸腺苷(adenosine diphosphate,ADP)、一磷酸腺苷(adenosine monophosphate,AMP)]含量,计算总腺苷酸(total adenine nucleotide...     

The Influence of Preburial Insect Access on the Decomposition Rate

Abstract: This study compared total body score (TBS) in buried remains (35 cm depth) with and without insect access prior to burial. Sixty rabbit carcasses were exhumed at 50 accumulated degree day (ADD) intervals. Weight loss, TBS, intra‐abdominal decomposition, carcass/soil interface temperature, and below‐carcass soil pH were recorded and analyzed. Results showed significant differences (p << 0.001) in decomposition rates between carcasses with and without insect access prior to burial. An approximately 30% enhanced decomposition rate with insects was observed. TBS was the most valid tool in postmortem interval (PMI) estimation. All other variables showed only weak relationships to decomposition stages, adding little value to PMI estimation. Although progress in estimating the PMI for surface remains has been made, no previous studies have accomplished this for buried remains. This study builds a framework to which further comparable studies can contribute, to produce predictive models for PMI estimation in buried human remains.     

Estimating the timing of long bone fractures: correlation between the postmortem interval, bone moisture content, and blunt force trauma fracture characteristics*

There is very limited knowledge about how long perimortem fracture characteristics persist into the postmortem interval (PMI). Therefore, in this study, 60 porcine long bones were exposed to natural taphonomic conditions and fractured with a steel bone breaking apparatus every 28 days throughout a 141-day period. Differences between macroscopic blunt force trauma fracture characteristics (fracture angle, surface morphology, and outline) were examined to determine if they varied over time or in relationship to bone moisture content (ash weight) and overall assessment. There are significant relationships between (1) PMI and percent ash weight (%AW), fracture surface, and fracture angle and (2) %AW and fracture surface and fracture angle. Bone moisture content correlates significantly with fracture morphology and other characteristics commonly used by forensic anthropologists to determine the timing of traumatic injuries. However, fracture characteristics normally associated with perimortem trauma can persist long into the PMI.     

人体死后肝细胞DNA含量与死亡时间关系的研究

目的研究人体死后肝脏细胞DNA含量变化与死亡时间的关系及影响因素。方法选取46例已知死亡时间的人体肝脏,根据离体肝脏所处的环境温度分为12—19％（A组）和20—27％（B组）两组,每组23例。在死后24～72h内每隔4h穿刺取肝组织1次,制成细胞悬液,经RNA酶消化,PI染色后,用流式细胞仪测定被检测细胞中含不完整DNA的细胞数所占百分比,所得数据经Exp032V1．2软件计算N值。结果死后24～72h肝细胞N平均值,A组从10．91％增至49．72％,B组从16．22％增至69．63％。两组N平均值随死亡时间的延长均逐渐增高,与死亡时间有相关性,A组r值为：0．598,B组r值为0．77357。并且建立了不同环境温度对应的回归方程。结论在不同环境温度下,死后24～72h内人体肝脏细胞DNA降解均随死亡时间的延长和环境温度的升高而逐渐加快,相关数据可望为死亡时间推断提供一定参考依据。     

人脾细胞核几何参数变化与早期死亡时间的相关性研究

目的运用图像分析技术探讨人脾脏细胞核几何参数变化与死亡时间的关系。方法选31例已知死亡时间的人离体脾组织,在死后36h内每h细胞学涂片、Feulgen-Vans染色,对人脾细胞核的异形指数等5个几何参数进行图像分析。结果脾脏细胞核异形指数在死后5～36h呈上升趋势,r=0.983,线性回归方程y=11.334x-33.339,面积、等效直径、平均直径、周长均与死亡时间无明显的相关性。结论异形指数能较客观地反映人脾细胞核DNA降解后的离散分布状况,与死亡时间有明显相关性,可能是推断早期准确死亡时间的较好形态学指标。     

硬脑膜厚度及生物力学参数时序性变化在死亡时间推断中的应用

目的研究人尸体硬脑膜厚度以及生物力学参数与死亡时间(postmortem interval,PMI)的关系,探讨其用于推断PMI的可行性。方法收集尸体检验的硬脑膜样本并按死后6h、12h、18h、24h、30h、36h、48h、60h、72h、84h、96h分组,统一制作成4.0cm×1.0cm的A、B两块试件。测量A试件厚度后检测极限载荷、最大力变形、抗拉强度、弹性模量、断裂力等生物力学参数,分别拟合厚度和生物力学参数值与PMI的回归方程,并通过验证组验证PMI预测值与实际值之间的差异。B试件经10%中性甲醛溶液固定后制备组织切片观察其形态学变化。结果死后6~96h,硬脑膜厚度逐渐减小,胶原纤维从排列清晰逐渐变为相互融合,细胞核数量逐渐变少;硬脑膜厚度、极限载荷、抗拉强度、弹性模量、断裂力呈时序性下降趋势,其中硬脑膜厚度、极限载荷、弹性模量、断裂力与PMI具有相关性(P<0.05)。回代检验中验证组PMI实际值和预测值之间差异无统计学意义(P>0.05)。结论人死后6~96 h的硬脑膜厚度、极限载荷、弹性模量、断裂力呈时序性变化,利用其与PMI的关系建立的回归方程可用于PMI推断。     

An Examination of the Transition of Fracture Characteristics in Long Bones from Fresh to Dry in Central Florida: Evaluating the Timing of Injury

It is important to conduct timing of injury research analyzing fracture characteristics at known postmortem intervals (PMI) because bone can retain fresh characteristics throughout the PMI. Defleshed pig (Sus scrofa) long bones were fractured weekly in two environments (full sun and shade) over 14 weeks in Central Florida and fracture characteristics were categorized (N = 136) for analysis. Results of analysis of variance (ANOVA) using time in weeks (PMI) as a dependent variable indicate significant relationships between PMI and Fracture Angle (p < 0.001), Fracture Surface (p < 0.001), and Fracture Outline (p < 0.001). Fracture characteristics associated with perimortem trauma (smooth Fracture Surfaces and curved or V‐shaped Fracture Outlines) were commonly observed. Analysis of fracture characteristics for each environment demonstrated similar patterns. Overall, the loss of only fresh fracture characteristics for each bone was noted earlier in the PMI for the Central Florida region than previously reported.     

Citrate Content of Bone as a Measure of Postmortem Interval: An External Validation Study

The postmortem interval (PMI) of skeletal remains is a crucial piece of information that can help establish the time dimension in criminal cases. Unfortunately, the accurate and reliable determination of PMI from bone continues to evade forensic investigators despite concerted efforts over the past decades to develop suitable qualitative and quantitative methods. A relatively new PMI method based on the analysis of citrate content of bone was developed by Schwarcz et al. The main objective of our research was to determine whether this work could be externally validated. Thirty‐one bone samples were obtained from the Forensic Anthropology Center, University of Tennessee, Knoxville, and the Onondaga County Medical Examiner's Office. Results from analyzing samples with PMI greater than 2 years suggest that the hypothetical relationship between the citrate content of bone and PMI is much weaker than reported. It was also observed that the average absolute error between the PMI value estimated using the equation proposed by Schwarcz et al. and the actual (“true”) PMI of the sample was negative indicating an underestimation in PMI. These findings are identical to those reported by Kanz et al. Despite these results this method may still serve as a technique to sort ancient from more recent skeletal cases, after further, similar validation studies have been conducted.     

组织中三甲胺-氮浓度变化与晚期PMI关系初探

目的探索死后尸体组织中三甲胺-氮(TMA-N)浓度变化规律及其与晚期死亡时间的关系。方法健康SD大鼠66只,颈椎脱臼法处死,随机分成11组,分别于死后即刻、1、2、3、4、5、6、7、8、9、10d取大鼠肌肉、肝脏和肾脏组织,用分光光度法检测TMA-N浓度,所得数据用方差分析比较组间差异性,并进行回归方程拟合。结果3种组织中TMA-N含量随死后时间延长而增加,肌肉于死后7d、肝脏和肾脏于死后8d达到高峰,之后有所下降,并均于死后10d再次升高,肝、肾组织之间TMA-N含量比较无统计学差异性。死后2~7d内,PM I与肌肉TMA-N浓度变化拟合度最高(R2=0.969);死后3~8d内,与肝肾中TMA-N浓度变化拟合度最高(R2=0.953)。结论死后组织中TMA-N含量变化与PM I有相关性,可望为晚期PM I推断提供参考,但肌肉与肝肾TMA-N含量变化规律存在一定差异,需选择最适时段以提高PM I推断的准确性。     

Sex‐ and Size‐Related Patterns of Carrion Visitation in Necrodes littoralis (Coleoptera: Silphidae) and Creophilus maxillosus (Coleoptera: Staphylinidae)

The estimation of postmortem interval (PMI) based on successional patterns of adult insects is largely limited, due to the lack of potential PMI markers. Sex and size of adult insects could be easily used for such estimation. In this study, sex‐ and size‐related patterns of carrion attendance by adult insects were analyzed in Necrodes littoralis (Coleoptera: Silphidae) and Creophilus maxillosus (Coleoptera: Staphylinidae). For both species, abundance of males and females changed similarly during decomposition. A slightly female‐biased sex ratio was recorded in N. littoralis. Females of N. littoralis started visiting carcasses, on average, one day earlier than males. There was a rise in size of males of N. littoralis at the end of decomposition, whereas for females of both species and males of C. maxillosus, no size‐related patterns of carrion visitation were found. Current results demonstrate that size and sex of adult carrion beetles are poor indicators of PMI.     

Citrate Content of Bone for Time Since Death Estimation: Results from Burials with Different Physical Characteristics and Known PMI

A recently introduced method to determine the postmortem interval (PMI) based on quantification of the citrate content in bone was applied on the temporal bones and femora of 20 individuals buried in wooden coffins (WO) and body bags (BB), respectively. Concerning known vs. calculated PMI, a significant difference between the temporal and the femur bone samples of the same individuals was observed in the BB group (p = 0.012). In contrast, differences were insignificant for the WO group (p = 0.400). Moreover, similar levels of underestimation of PMIs resulted from the analysis of the femora for both burial groups (p = 0.247). Also, there was consistently less citrate preserved in the flat temporal bones as compared to the femora, indicating that the cortical layer of the long bones should be preferentially employed for citrate‐based PMI estimations. The results call for additional research on subsurface‐buried and surface‐deposited remains to enhance the accuracy of the published PMI equation.     

Bioelectrical Impedance as a Technique for Estimating Postmortem Interval,,

Estimation of postmortem interval (PMI) is a critical component of death investigation. A cadaver can be hypothesized to be a resistor–capacitor (RC) circuit the impedance (Z) of which changes in a quantifiable manner as the cadaver decomposes. This hypothesis was tested using bioelectrical impedance analysis (BIA) equipment to apply a current with a fixed amplitude at a single frequency to four cadavers over time and measuring two components of Z, resistance (R) and reactance (X_c). Quadratic regression analysis between Z and accumulated degree days (ADD) showed a statistically significant parabolic relationship. The parabolic relationship poses an initial challenge to the use of the method, and additional research is needed to address this issue. However, the results of the reported research support the hypothesis that Z measured using BIA has a relationship to PMI.     

Temperature‐Dependent Postmortem Changes in Human Cardiac Troponin‐T (cTnT): An Approach in Estimation of Time Since Death

Estimation of time of death is an indispensible requirement of every medico‐legal autopsy, but unfortunately, there is not a single method by which it could be determined accurately. This study focused on the temperature‐dependent postmortem degradation of cardiac troponin‐T and its association with postmortem interval (PMI) in human. The analysis involved extraction of the protein, separation by denaturing gel electrophoresis (SDS‐PAGE), and visualization by Western blot using cTnT‐specific monoclonal antibodies. The area of the bands within a lane was quantified by scanning and digitizing the image using Gel Doc (Universal Hood). The results indicate a characteristic banding pattern among human cadavers (n = 6) and a pseudo‐linear relationship between percentage of cTnT degradation and the log of the time since death (r > 0.95), which can be used to estimate the postmortem interval. The data presented demonstrate that this technique can provide an extended time range during which PMI can be more accurately estimated.     

外温变化下小鼠肝细胞18s rRNA降解与死亡时间关系研究

目的探讨在外界环境温度变化条件下,小鼠肝细胞18s rRNA降解与死亡时间的关系。方法小鼠断颈处死后置于10℃、15℃、20℃、25℃、和30℃温度下保存;从死后6h至72h,每6h分别提取肝细胞组织中总RNA。利用实时荧光定量PCR检测18s rRNA循环阈值(Ct值)的变化。应用插值函数进行分析拟合,建立死亡时间推断方程。结果各温度组Ct值随死亡时间延长均呈上升趋势,对所得数据进行插值拟合,得到一定温度变化区间内(10℃~30℃),Ct值变化与PMI关系的三元五次曲面方程:f(x,y)=-426.9+30.82x+44.48y-1.297x~2-1.837xy-1.388y~2+0.034 38x~3+0.038 17x~2y+0.038 67xy~2+0.028 77y3-0.000 612 9x~4-3.897e~(-7)x~3y-0.001 223x~2y~2+0.000256 6xy3-0.000 537 4y~4+3.606e~(-6)x~5-2.846e~(-6)x~4y+1.009e~(-5)x~3y~2-3.439e~(-6)x~2y3-2.556e~(-7)xy~4+2.664e~(-6)y~5(r2=0.999 4)。结论在外界温度变化条件下,小鼠肝细胞18s rRNA降解与死亡时间关系符合三元五次方程分布,利用插值函数拟合的方法可在外界环境温度变化条件下进行死亡时间推断。     

Comparing Homicide‐Suicides in the United States and Sweden

Research on homicides followed by suicides has largely relied on very localized samples and relatively short time spans of data. As a result, little is known about the extent to which patterns within cases of homicide‐suicides are geographically specific. The current study seeks to help fill this gap by comparing twenty years of homicide‐suicide data for Sweden and a large U.S. county. Although some of the underlying patterns in the two countries are similar (e.g., decreasing rates), a number of important differences emerge, particularly with respect to incidence, weapons used, perpetrator age, and relationship of the perpetrator to the victim.     

不同温度下大鼠脑组织RNA降解与早期PMI的相关性

目的探讨大鼠脑组织8种RNA指标,在不同温度下的表达水平与早期死亡时间(PMI)的相关性。方法将222只SD大鼠随机分为对照组(死后0 h)和4个实验组,实验组断颈处死后分别置于5℃、15℃、25℃和35℃的环境中,于死后1~24 h内9个时间点提取脑组织RNA,利用实时荧光定量PCR技术检测8种RNA指标(β-actin、GAPDH、RPS29、18S rRNA、5S rRNA、U6 snRNA、miRNA-9及mi RNA-125b)的表达水平,ge Norm软件选取合适内参,SPSS软件对内参标准化RNA指标进行回归分析,R软件构建推断PMI的数学模型,另选6只已知PMI的SD大鼠予以验证。结果 5S rRNA、miR-9和mi R-125b表达稳定,可作为内参指标。β-actin和GAPDH具有良好的时序性降解规律,在24 h内随PMI延长不断降解。R软件拟合得ΔCt值随PMI和温度变化的数学模型可用以推断PMI。运用β-actin和GAPDH验证模型的平均误差率分别为14.1%和22.2%。结论β-actin和GAPDH表达水平与PMI和环境温度相关性良好。本研究建立的数学模型可为温度变化条件下的早期PMI推断提供参考。