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.     

大鼠肌肉中微生物ATP含量及其在死亡时间推断中的应用

目的 研究死后大鼠肌肉组织中微生物ATP浓度变化及其与死亡时间(postmortem interval,PMI)的关系. 方法取健康SD大鼠处死,死后不同时间取肌肉组织,用生物发光法检测微生物ATP浓度,对所得数据进行统计学处理.结果 死后肌肉组织中微生物ATP含量随时间延长而增加,于7d达到高峰,随后逐渐降低,并于10d再次略微升高.PMI在0～9d内与肌肉中微生物ATP含量变化拟合最优.以PMI为自变量的三次多项式回归方程为:y=0.020x3-0.166x2-0.666x+13.412(r2=0.989,P<0.01).结论 死后肌肉组织中微生物ATP含量变化可用于PMI推测;本检测方法所需检材量小,不受组织自身降解的影响.     

死亡时间推断的研究与进展

本文综述了组织学、组织化学、细胞分子生物学在死亡时间推断方面的研究成果及最新进展,随着死亡时间的延长,组织细胞、体液成分、生物大分子均出现规律性变化,并与死亡时间高度相关,可用于死亡时间的推断。     

The Red Swamp Crayfish Procambarus Clarkii (the Louisiana Crayfish) as a Particular Scavenger on a Human Corpse

An 85-year-old man was found deceased floating in an irrigation ditch 18 days after his disappearance. During crime scene investigation, specimens of the red swamp crayfish Procambarus clarkii were found in proximity of the body. The feeding activity of these nonendemic crayfishes contributed to the formation of specific injuries on the body and in the production of a large substance defects inside the corpse. The aim of this paper was to illustrate the scavenging activity of P. clarkii on a human body and highlight the potential postmortem artefacts caused by this species. This is the first report on a real case of postmortem injuries produced by P. clarkii crayfishes on a submerged human body. So far, crustaceans are not considered useful for the estimation of the minimum postmortem interval. However, the important modifications on the corpses deriving from the activity of these animals should be kept in consideration.     

Modeling Temperature Variations Using Monte Carlo Simulation: Implications for Estimation of the Postmortem Interval Based on Insect Development Times*†

The association between insect development and temperature is well established. Thermal summation using accumulated degree-day measures is commonly used. However, the time at which evidence is collected is important in these estimates. The aim of this study was to provide a simulated model of the effect of temperatures on six dipteran species commonly associated with cadavers, from the death scene to the refrigerator, and finally at the time of autopsy. Temperatures measurements were sampled over a 16-month period from the external environment (external to the mortuary), within the mortuary refrigerator, and within the mortuary autopsy suite. Monte Carlo simulation using accumulated degree-days (ADD) was used to estimate the variations based on the mean and standard deviation of the temperature measurements. It was found that there was a negative correlation between the base temperature of the fly species (lowest temperature at which the flies will survive) and developmental likelihood. Species with high base temperatures (Chrysomya albiceps, Chrysomya chloropyga, and Musca domestica) were less likely to continue development in refrigerators than species with lower base temperatures (Lucilia sericata and Piophila casei). The findings of this study highlight the importance of recording temperature measurements and the period of refrigeration on PMI estimation especially when continued development occurs in spite of a period of cooling of the insect evidence.     

Evaluation of direct PCR for routine DNA profiling of non-decomposed deceased individuals

Forensic DNA profiling is a standard method used in the attempt to identify deceased individuals. In routine investigations, and if available, the preferred sample type is usually blood. However, this requires the invasive re-opening of the body, days or weeks after the autopsy, which is undesirable in resource-constrained mortuary settings. Motivated by the ease of sampling as well as reduced health and safety risks, this study aimed to establish the success rate of generating a full DNA profile on first attempt from buccal swab lysates using a direct PCR approach. Buccal swab samples were collected from 100 unidentified deceased males, and were subjected to direct DNA profiling with use of the Promega PowerPlex® Y23 Kit. At the time of sample collection, these individuals had been stored for between 1 and 887 days. This study shows that full DNA profiles were initially obtained from 73% of samples, which constitutes the first empirical data pertaining to first time success rates of direct PCR from post-mortem buccal lysates. Further investigation of partial and failed DNA profiles using real-time PCR showed that samples did not contain PCR inhibitors, DNA was not degraded, but DNA concentration was particularly low. Repeating DNA profiling with increased lysate input and extra PCR cycles yielded an additional six full DNA profiles, resulting in an overall success rate of 79%. Overall, DNA profile success rate was not associated with the duration of storage (p = 0.387). Lastly, massively parallel sequencing with the ForenSeq™ Signature DNA Prep kit provided more informative profiles for three additional samples. These results indicate that blood should therefore remain the sample of choice in a post-mortem setting, yet buccal lysates hold potential to be optimised further, which may ease the human identification workflow.     

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...     

大鼠死后脑组织的傅里叶变换红外光谱变化

目的应用傅里叶变换红外（Fourier transform infrared．FTIR）光谱技术分析大鼠死后脑组织随死亡时间推移的化学变化过程,为死亡时间推断的研究提供新的途径与数据。方法大鼠断颈处死后置于（30±2）℃环境下,在不同时间点提取大鼠脑皮质．运用FTIR光谱仪检测不同化学基团的变化。结果随着死亡时间的推移,大鼠脑组织FTIR光谱的主要吸收峰峰位没有明显变化．而其峰强有明显差异：（1）与核酸有关的谱带的相对峰强呈明显下降趋势;（2）酰胺Ⅰ、Ⅱ的峰强比（I1647/I1541）呈下降趋势;（3）1456和1398cm^-1谱带的峰强各自呈下降和上升趋势;（4）2852、2871、2923和2958cm^-1谱带的峰强相对于1647cm^-1而言．呈上升趋势。结论脑组织可以作为FTIR光谱技术分析死亡时间的适用检材。     

脑组织与其相关分析推断死亡时间的研究进展

推断死后间隔时间(postmortem interval,PMI)一直是法医学鉴定中需要解决的重要问题之一.可用于推断PMI的尸体检材有很多种,脑组织因其独特的解剖学位置与生理功能,是推断PMI的重要检材之一.本文从三个方面将根据脑组织推断PMI的方法进行综述,包括了通过脑组织的温度、形态特点等尸体现象推断PMI;通过...     

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。