Postmortem behavior of the rheobase

Own investigations on the postmortem rise of muscular threshold were conducted on 20 bodies with exactly known time of death. Muscular contraction was objectified using a sensitive force transducer. The muscle was excitated using rectangular impulses of 1 second duration of a current intensity which produces a force of muscular contraction of 2.5 mN. These excitations were continued over the postmortem interval until a current intensity of 80 mN doesn't cause a contraction of 2.5 mN any more. Investigations were mainly performed at the thenar muscles. There is a linear relationship between ln of muscular threshold (current intensity) and the time since death (r = 0.965). For any case the linear regression line between ln of muscular threshold and time since death was calculated. With mean values for slope and intercept the time of death was calculated for each measured threshold. Extrapolation of the time since death with mean values also for the slope reveals a much more precise estimation of the time since death than an extrapolation with an individual slope as proposed by Joachim and Feldmann (1980). The method was proved on a random sample of 8 practical cases. The real time since death was always within the 95%-limits of confidence of the extrapolated time since death.     

Factors influencing the precision of estimating the postmortem interval using the triple-exponential formulae (TEF). Part II. A study of the effect of body temperature at the moment of death on the postmortem brain, liver and rectal cooling in 117 forensic cases

The temperatures of three body sites, namely, the brain, liver and the rectum as well as the temperature of the environment were continuously monitored, every 5-10 min, in 117 forensic cases commencing soon after death and in most cases, within 45 min postmortem. The body temperature at the moment of death was empirically determined by a computer-based extrapolation method. Thus, temperature data for the first 3h of each body site were fitted to single-exponential equations and the fitted curve was extrapolated backwards to obtain the intercept on the Y-axis (the temperature axis). The effect of body temperature at the moment of death on postmortem cooling rate is examined and factors influencing body temperature at death are discussed. Forensic fatalities associated with hyper and hypothermia are reviewed briefly.     

Preliminary quantitative investigation of postmortem adipocere formation

The accurate determination of postmortem interval (PMI) using the formation of adipocere presents a significant challenge to forensic scientists interested in determining the time of death. Several attempts have been made to determine the time since the occurrence of death. However, up to date, this has been difficult because previous approaches have been mainly qualitative, focusing on the later stages of degradation processes. This work presents preliminary results of an experimental model of postmortem adipocere formation using liquid chromatography. Three pig cadavers were submerged in distilled water, chlorinated water, and saline water. Fresh specimens resulting from the degradation in the subcutaneous fat were obtained from the pigs at two-week intervals for a period of ten weeks, and were subjected to chromatographic analysis. By correlating the ratio of the disappearance of hydrolyzed fatty acids with the formation of hydroxystearic and oxostearic acids after death, a simple, quantitative analytical method was developed for the determination of PMI. Experimental observation of the chemistry of adipocere formation indicated that adipocere can be formed only a few hours after an incidence of death and this continues until the saturation of oleic acid degradation after several weeks. Different time courses were obtained for cadavers immersed in distilled, chlorinated, and saline water, respectively. This work has not in any way solved the time since death problem. But it may be an approach to the problem that has not been adequately explored.     

Amount of postmortem bleeding: an experimental autopsy study

An experimental autopsy study was performed on 64 cases (55 male, 9 female; average age 51.5 +/- 16.2 years) of sudden natural (38 cases) and asphyxic deaths (26 cases). The study objective was the amount of postmortem bleeding from postmortem cutting of the thoracic aorta, related to the time since death. The amount of postmortem bleeding ranged from 100 to 1300 cm, 440.6 +/- 268.1 cm on average. The time since death up to the autopsy time ranged from 4 to 72 hours, 19.4 +/- 12.9 in average. A statistically significant correlation between the amount of postmortem bleeding and postmortem time interval was stated: Pearson correlation test value r = -0.461 (P = 0.000): the shorter the time interval, the larger the amount of bleeding. The formula of linear regression was estimated according to this correlation: amount of postmortem bleeding (cm) = -9.571 x time since death (h) + 626.659. This proves that the amount of postmortem bleeding (eg, from aortic blunt rupture) could be about 620 cm.     

Factors affecting postmortem tooth loss

Unassociated human bones are a particular problem during the exhumation of mass graves and a factor that limits anthropological and paleopathological analyses from archaeological contexts. Extensive anthropological literature has focused on the complex taphonomic factors that influences bone assemblages, but little attention has been paid to postmortem tooth loss and factors affecting this process. The following study focuses upon the influence of different factors on postmortem tooth loss. Three samples were investigated in the study: a medieval church cemetery containing 110 individual skeletal remains, and two samples from a series of mass graves made within the same time period in 1999, containing 402 bodies. The frequency of postmortem tooth loss was analyzed relative to postmortem interval for each sample, excavation methods, age distribution, and presence of bone loss associated with periodontal disease. Our results indicate that the degree of alveolar bone loss significantly affected both antemortem and postmortem tooth loss and that the frequency of postmortem tooth loss has the strongest correlation to time since death. These findings suggest that additional care should be taken when exhuming remains from older contexts.     

Supravital electrical excitability of muscles

A new method of postmortem electrical stimulation of muscles, measuring the force of the reaction against time, is presented. Preliminary investigations have yielded the following results: The maximum force of reaction in response to a definitive stimulation, measured by a sensitive force transducer, decreases in proportion to the post mortem interval. Using this method, the mechanical reactions of muscles by electrical stimulation can be demonstrated over a much longer postmortem period as these movements are visible. The duration of postmortem reaction of different muscles seems to be much more uniform than was previously assumed. Occasionally, reactions of the M. orbicularis oculi can be seen for the longest time. The basal muscular tonus changes relative to time. The time course of a single force reaction also changes relative to the postmortal interval: the reaction becomes slower. It has been theoretically established that measurement of influencing factors such as temperature and pH in the tested muscle will enable the time of death to be more precisely estimated.     

傅里叶变换红外光谱技术在死亡时间推断中的运用

死亡时间(postmortem interval,PMI)推断是命案现场首先要解决的重要问题之一,因此法医学者运用了大量的技术和统计学方法试图精确推断PMI.由于PMI推断受到外部、内部、死亡前和死亡后等多种因素影响,既往多种方法均存在局限性.傅里叶变换红外(Fourier transform infrared,FTIR)光谱技术已应用于蛋白质、核酸、碳水化合物的纯品物质研究上,近年来也被广泛用于研究复杂的细胞和组织.功能强大的计算机软件可以对光谱变换、平滑、基线校正、归一化等进行处理,使FTIR光谱仪对样本的定量研究成为可能,并从分析化学领域推广到生物学和临床医学研究.本文综述了FTIR光谱原理及其在生物医学中的应用,并着重阐述死后尸体组织的FTIR光谱学变化及在PMI推断中的应用价值.     

The application of differential thermal analysis and thermogravimetric analysis to dating bone remains.

Thirty-four samples of bone remains of known time since death were studied by using DTA, TGA, and derivative-TGA techniques. The DTA patterns enable us to distinguish recent from old (more than 100 years) bones. The TGA curve is also significant for an extreme series. Both DTA and TGA curves show a correlation that allows us to obtain patterns with high significance for the extreme series. They also make evident the decomposition grade that bone organic material undergoes during the postmortem putrefactive process.     

Estimation of the time since death: sudden increase of ambient temperature

This work presents a procedure for the postmortem interval estimation in the presence of a rapid increase of ambient temperature occurred during the cooling phase. The resulting disturbance produced on the cooling curve is proved to obey a two-exponential law and is removed from the actually measured body temperature. This yields a theoretical/modified body temperature, which enables the estimation of the time since death by means of the standard Nomogram method.     

Is there recent progress in the estimation of the postmortem interval by means of thanatochemistry?

Numerous methods have been proposed in the last 60 years for the determination of the time since death by chemical means. Many of them were reviewed by Schleyer in his monograph on the determination of the time since death by means of thanatochemistry about 40 years ago and none of these early methods has gained any practical value since they do not meet the demands in practice (being precise, reliable, giving an immediate result). While the earlier studies were mainly carried out on blood and cerebrospinal fluid (CSF) since the late 60s most investigations have been performed on vitreous humor (VH). This is mainly due to the fact that vitreous humor is topographically isolated and well protected, and thus, autolytic changes proceed slower compared to blood and CSF. The most studied parameter in VH is potassium and even nowadays reports on the postmortem rise of vitreous potassium are published, proposing new analytical methods or statistical evaluations. Chemical parameters studied for the determination of the time since death have to be differentiated according to the underlying process (catabolism, metabolic processes, pure autolysis and diffusion, putrefactive changes). In the present paper, recent studies on thanatochemistry are discussed regarding the underlying process, the analytical methods (for instance H magnetic resonance spectroscopy (1H MR spectroscopy), immunohistochemistry), the studied fluid compartment, the statistical evaluation and the precision of death time estimation. The value of chemical methods for the determination of the time since death is up to now very limited. This is supported by the fact that field studies on the reliability and precision of death time estimation by chemical means are still scarce in the literature.     

Comparison of morphological changes in white blood cells after death and in vitro storage of blood for the estimation of postmortem interval.

Estimation of the time of death is one of the most important problems for forensic medicine and law. Physical and chemical postmortem changes are evaluated together while estimating the time of death.In this study, in vitro storage and postmortem changes of white blood cells were aimed to be compared within the given postmortem interval, and a follow-up study was carried out. Blood smears which were obtained from 10 non-refrigerated cadavers (experimental group) and from 40 hospital patients (control group) have been evaluated to observe and compare changes during the in vitro storage and postmortem degenerative morphological changes that white blood cells undergo throughout the given postmortem intervals. The samples were examined by using a light microscope, and blood cells were differentiated by staining blood films with May-Grunwald stain, followed by Giemsa stain. Identifiable degenerated eosinophils and monocytes were first examined at 6h of death and the in vitro storage, and they were unidentifiable beyond 72 h of storage. Identifiable degeneration of neutrophils were first examined at 6h of death and storage while unidentifiable beyond 96 h of storage. Identifiable degeneration of lymphocytes were first examined at 24h of death, and they were still identifiable beyond 120 h.Cellular changes of leukocytes can be useful in the 6-120 h for estimating the time of in vitro storage, and the findings match during the first 21 h for both experimental and control groups. Finally, this follow-up study and the comparison will also be carried out for a longer postmortem interval, and other specific hypothesis that relate cellular changes in tissues other than blood with time since death are various points that needs to be studied.     

尸检样本乙醇分析结果的解释策略

由于死后各种复杂的人为现象的存在,使得建立死后血液酒精含量(BAC)和死亡时醉酒状态之间的关系十分困难。在日常检案中必须考虑细菌污染、发酵是否引起死后乙醇再合成,死亡时胃中未被吸收的乙醇是否向周围组织以及血中扩散等问题。本文总结了关于死后乙醇分析及结果解释相关问题的研究文献,旨在为从事法医毒物学乙醇分析的同行在调查此类案件时提供良好的开端。     

Factors affecting decomposition and Diptera colonization.

Understanding the process of corpse decomposition is basic to establishing the postmortem interval (PMI) in any death investigation even using insect evidence. The sequence of postmortem changes in soft tissues usually gives an idea of how long an individual has been dead. However, modification of the decomposition process can considerably alter the estimate of the time of death. A body after death is sometimes subject to depredation by various types of animals among which insects can have a predominant role in the breakdown of the corpse thus, accelerating the decomposition rate. The interference of the insect community in the decomposition process has been investigated by several experimental studies using animal models and very few contributions directly on cadavers. Several of the most frequent factors affecting PMI estimates such as temperature, burial depth and access of the body to insects are fully reviewed. On account of their activity and world wide distribution, Diptera are the insects of greatest forensic interest. The knowledge of factors inhibiting or favouring colonization and Diptera development is a necessary pre-requisite for estimating the PMI using entomological data.     

Estimation of postmortem interval using the protein marker cardiac Troponin I

The importance of determining the time since death is crucial to criminal, civil and forensic cases. A technique exploiting the degradation of a protein, cardiac Troponin I (cTnI), to estimate the postmortem interval (PMI) was investigated. Cardiac Troponin I is a basic regulatory protein found as part of a ternary complex responsible for calcium dependent muscle contraction. An efficient extraction protocol to analyze the banding pattern of cTnI in postmortem tissue was developed. The analysis involves extraction of the protein, separation by denaturing gel electrophoresis (SDS-PAGE) and visualization by Western blot using cTnI specific monoclonal antibodies. A bovine model was used to develop and optimize the protocol. The homology of cTnI amongst mammalian species allows for the cross-reaction of human anti-cTnI antibodies with bovine cTnI. The results indicate a characteristic banding pattern amongst human cadavers (n=6), a pseudo-linear relationship between percent cTnI degraded and the log of the time since death (r>0.95), and a qualitative degradation band pattern that in a simple comparative analysis with a standard human heart (known time since death) can be used to estimate the postmortem interval. The degradation-banding pattern of tissue cTnI is useful in the determination of the early postmortem (pm) interval (0-5 days). Overall, this technique offers advantages such a wide postmortem interval, measurable degradation pattern, a temporal semiquantitative relationship and manageable temperature dependence over direct temperature methods.     

死亡大鼠看家基因mRNA时序性降解的组织差异性研究

目的研究死亡大鼠看家基因mRNA时序性降解的组织差异性,评价其用于死亡时间推断的价值。方法SD大鼠20只分为死后0、1、3、5、7d共5组,脊椎脱臼法处死大鼠,提取大鼠心、肝、脾、肺、肾、脑组织,在相应时间段提取RNA,应用一步法RT-PCR技术检测各组织中看家基因GAPDHmRNA和β-actinmRNA的水平,Vilber凝胶图像分析系统测定扩增产物IOD值,SPSS10．0统计软件对数据进行方差分析。结果GAPDHmRNA、β—actinmRNA扩增产物相对灰度与积分光密度值随死后经过时间的延长而逐渐减小,且与死亡时间显著相关,大鼠脾脏和脑组织GAPDHmRNA和β-actinmRNA在死后5d内可检出,心脏和肾脏在死后3d内可检出,而肝脏和肺脏GAPDHmRNA和β-actin mRNA降解较快,仅在死后1d内可检出。结论脑组织和脾脏中mRNA稳定性较好,适用于PMI特别是晚期PMI的推断。除环境温度外,环境湿度也是死亡时间推断中的重要影响因素。     

Multiple-probe thermography for estimating the postmortem interval: II. Practical versions of the Triple-Exponential Formulae (TEF) for estimating the time of death in the field

A simple, reliable, and relatively accurate method for estimating the time since death is described. It is based on the Triple-Exponential Formulae (TEF), which are devised for the first time in this study. The postmortem cooling rate of the brain, liver, and rectum in 117 forensic cases were investigated (Part I). The method can be used in the field as a computer program, reference graph, or reference chart-ruler. The program is simple and can easily be run by any user. There are six reference graphs representing the average brain, liver, and rectal cooling curves for naked and covered body groups. The ruler is designed for the rectal cooling curves for covered and naked bodies. This method requires one temperature measurement of the chosen body site and the environment. The postmortem interval is estimated as a probable value +/- a possible range of time estimates with a built-in confidence limit.     

Practical experiences with the determination of cadaver age by evaluation of bacterial metabolic products

In an experiment a corpse had been kept at room temperature (16 degrees-23 degrees C) for 1163 h. At regular intervals brain samples were taken and the content of free amino acids and related compounds was determined by column chromatography. It could be demonstrated that in a period of 4-20 days postmortem the age of the corpse could be calculated from the concentrations of alpha-aminobutyrate (ABU), gamma-aminobutyrate (GABA), and glutamic acid (GLU) in brain employing the previously [5] presented formula: (formula; see text) T is the postmortem time lapse (days). ABU, GABA, and GLU are the concentrations (mumol/g) wet tissue of the corresponding amino acids. During this postmortem interval there is nearly a linear correlation; from this interval a correct assignment between concentrations and time cannot be given. The determination method is in the range of about 15 degrees-25 degrees C (guarantees bacterial growth and metabolism) independent of ambient temperature. The brain samples (cortex or parts of the putrified brain mush) can be taken without any special precaution during normal autopsy. The results of the experiment (in Fig. 1) were supported by some practical cases where the time lapse since death was well (in Fig. 1) or reasonably (in Fig. 1) known. These results suggest that this method allows in many cases the determination of the age of a corpse found in a warm environment (approximately 15 degrees-25 degrees C) approximately 4-20 days after death.     

Postmortem transport of gastric contents?

For the determination of the time since death, the distribution of the last meal in the stomach and small bowel may be of great importance. It may be even more difficult to estimate the time if there is a possibility that postmortem peristaltic emptying of the gastric content occurs, as has been claimed. Radiological control immediately after death by means of applying barium sulfate to the stomach, however, revealed no evidence of peristaltic emptying of the gastric content after death.     

The use of absolute refractory period in the estimation of early postmortem interval

The estimation of the time since death (postmortem interval) is one of the most difficult problems in forensic pathology. Most methods currently employed use temperature-based algorithms intended to model the cooling of the body after death and thus estimate the postmortem interval. These methods are subject to considerable inaccuracy but their reliability can be improved if a range of other observed criteria such as lividity and rigor are also taken into consideration. The aim of the present study was to investigate the feasibility of using the absolute refractory period as an adjunct to the estimation of postmortem interval. The relationship between the `postmortem interval' and the `duration of absolute refractory period' was investigated using the rat sciatic nerve. A strong correlation between the duration of the absolute refractory period and the postmortem interval was observed. When both absolute refractory period and temperature were used in conjunction, the strength of this correlation was increased.     

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.