Comparison of chemical methods for determining postmortem interval

Accurate determination of postmortem interval (PMI) is a problem for the forensic thanatologist, especially in unwitnessed deaths. A number of objective chemical methods for determining PMI have been developed, the most widely used being accumulation of potassium in the vitreous humor. The authors previously have reported a chemical method for determining PMI from the predictable accumulation or clearance of the dopaminergic metabolite 3-methoxytyramine (3-MT) in the putamen of the brain. They have extended their previous study to compare directly the accuracy of determining PMI from the level of 3-MT in putamen with the level of potassium in vitreous humor. The data indicate that 3-MT is at least as accurate as, if not more accurate than, potassium accumulation in vitreous humor, although 3-MT levels can be affected by the cause of death and drugs present at the time of death. Nevertheless, determination of both the 3-MT and potassium levels can afford the most accurate method of determining PMI; preliminary nomograms for determining PMI from both variables are presented.     

Corneal‐Smart Phone: A novel method to intelligently estimate postmortem interval

The changes of postmortem corneal opacity are often used to roughly estimate the postmortem interval (PMI) in forensic practice. The difficulty associated with this time estimate is the lack of objective means to rapidly quantify postmortem corneal changes in crime scenes. This study constructed a data analysis model of PMI estimation and implemented an intelligent analysis system for examining the sequential changes of postmortem corneal digital images, named Corneal‐Smart Phone, which can be used to quickly estimate PMI. The smart phone was used in combination with an attachment device that provided a darkroom environment and a steady light source to capture postmortem corneal images. By segmenting the corneal pupil region images, six color features, Red (R), Green (G), Blue (B), Hue (H), Saturation (S), Brightness (V) and four texture features Contrast (CON), Correlation (COR), Angular Second Moment (ASM), and Homogeneity (HOM), were extracted and correlated with PMI model. The results indicated that CON had the highest correlation with PMI (R² = 0.983). No intra/intersubject variation in CON values were observed (p > 0.05). With the increase in ambient temperature or the decrease in humidity, the CON values were increased. PMI prediction error was <3 h within 36 h postmortem and extended to about 6–8 h after 36 h postmortem. The correct classification rate of the blind test samples was 82%. Our study provides a method that combines postmortem corneal image acquisition and digital image analysis to enable users to quickly obtain PMI estimation.     

Estimation of postmortem interval. Temperature-correction of extracellular abdominal impedance during the first 21 days of death

Extracellular impedance of the intact abdomen of rats increased from 79.0+/-7.4Omega, 1h postmortem (i.e. 0.04 day), to 130.5+/-14.4Omega at postmortem interval (PMI)=1 day. Impedance then decreased with time, reaching 64.2+/-9.9Omega at PMI=21 days. The time taken for mean abdominal impedance to decrease below the value at PMI=0.04 day averaged 16 days. It is therefore impossible, using extracellular abdominal impedance alone, to distinguish (in terms of interpolating PMI) between numerically equal impedances on the rising and falling phases of curves depicting impedance as a function of PMI.Correction of measured impedances to their theoretically-predicted values at an arbitrarily chosen temperature of 40 degrees C appreciably diminished the magnitude of the increase in impedance following death. Thus, temperature-corrected abdominal impedance increased from 56.2+/-4.8Omega at PMI=0.04 day to 59.5+/-6.2Omega at PMI=1 day. Impedance then decreased, reaching 29.2+/-4.1Omega at PMI=21 days. The time taken for mean, temperature-corrected abdominal impedance to decrease below the value at PMI=0.04 day averaged 3 days (as opposed to 16 days (see above) in the absence of temperature-correction).These findings are believed to improve the usefulness of extracellular abdominal impedance as a potential tool for estimation of postmortem interval.     

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 based on the third component of complement (C3) cleavage

To estimate postmortem interval (PMI), the spontaneous conversion of the native third component of complement (C3) to its derived fragments in whole blood was studied by crossed immunoelectrophoresis. C3 cleavages in vitro at different temperatures showed that the incubation of whole blood at a higher temperature led to a faster conversion of beta 1C (native C3) to beta 1A (C3c). In cadaveric blood, we found a significant positive correlation between percentage of C3 cleavage and PMI. From these results, it is possible to estimate PMI from the ratios of C3 cleavage.     

家兔死后红细胞内钾钠离子含量与死亡时间的关系

研究了40只家兔死后不同时间心血红细胞内钾钠离子含量变化及红细胞膜Na+－K+－ATP酶活性。发现红细胞内钾离子含量随死亡时间增加呈线性下降（r=-0．829,P＜0．025）。在死后0－48小时,红细胞内钾离子含量与死亡时间显著相关。红细胞膜Na+－K+－ATP酶活性在死后48小时无显著变化。     

Vitreous humor chemistry: the use of potassium concentration for the prediction of the postmortem interval

Upon review of the literature, extensive disagreement was found as to the usefulness of vitreous humor potassium concentration as a predictor of the postmortem interval (PMI). A pilot study of 1427 cases was performed to address this problem. The requisite statistical analysis for the prediction of PMI is inverse prediction. The 95% inverse prediction interval was found to be approximately +/- 20 h. The linear regression equation for the data was y = 0.238 chi + 6.342, with a coefficient of determination (r2) of 0.374. This r2 value means that 62.6% of the variation of potassium is unaccounted for by the variation in PMI. Further studies are required to attribute this unaccounted variation to quantifiable factors. This would narrow the inverse prediction interval and enable vitreous potassium to be a useful aid in the prediction of PMI.     

家兔死后眼玻璃体液消光度与死亡时间关系研究

目的 为寻找一种精确推定死亡时间的方法。方法 应用 754分光光度计,在 420nm波长下,检测了 48只家兔死后不同时间的眼玻璃体液消光度,探讨其与死亡时间的关系。结果 眼玻璃体液消光度（ X）与死亡时间（ Y）呈线性正相关（ r=0.983 27, P< 0.05）,在死后 0～ 72小时,眼玻璃体液消光度与死亡时间存在回归关系（ F=116.54, P< 0.05）,直线回归方程为： Y = 453.30X＋ 0.75 [Y为死亡时间 (PMI),单位为小时; X为眼玻璃体液消光度 ]。结论眼玻璃体液消光度的测定可作为推断死后 72小时内死亡时间的参考指标之一。     

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.     

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。     

大鼠死后心肌细胞DNA含量与死亡时间关系的进一步研究

目的研究机体的细胞核内DNA含量与死亡时间的关系。方法本实验通过计算机图像系统,选择核面积、积分光密度等7种参数,研究了15只大鼠心肌细胞在死后25～49h细胞核DNA含量的变化规律。结果心肌细胞DNA含量测定适合相对较长死亡时间的推断。结论应用计算机图像分析技术测量机体死后心肌细胞DNA含量将有可能成为推断死亡时间精确、客观的新方法。     

组织RNA检测用于死亡时间推断的研究进展

近几年来利用RNA的降解程度来推断死亡时间已逐渐成为法医学研究热点.本文复习相关研究文献,对大鼠不同组织(脑组织、心脏组织、肝脏组织和肾组织等)中RNA在推断死亡时间的具体应用方法做出总结,归纳出不同组织中的各类RNA在推断死亡时间方面的适用范围,以及对此种方法在推断死亡时间的过程中产生的问题及可行性的解决方法.     

Enzymehistochemical and immunohistological changes of skeletal muscle motor end-plates and muscle fibers and their relation to the time of death

In order to investigate the relationship between the retrograde changes of the skeletal muscle and the time of death in various postmortem intervals (PMI), a systemic study of the enzymehistochemical activity of AChE, SDH, LDH, Ca(2+)-ATPase and the immunohistochemical reaction of SYN in motor end-plates and muscle fibers was conducted in rats under different temperatures and at various PMI. The results were analyzed and compared by an image processing system. It was found that these changes were related to the PMI, especially AChE changes. The AChE could be used as a sign-enzyme of skeletal muscle to date death.     

蛋白质降解与死亡时间推断的初步研究

目的观察大鼠肝脏肌动蛋白、微管蛋白在死后不同时间的降解情况,为死亡时间的推断寻找客观依据。方法大鼠麻醉致死后置于21℃温度控制系统模拟死后18d的改变,在不同时间点剪取肝脏组织抽提蛋白质,利用westernblot技术检测肌动蛋白、微管蛋白的降解变化并对产物进行半定量分析。结果大鼠肝脏肌动蛋白在死后8d尚可检测,死亡10d后检测不到;在死后2d,α微管蛋白已检测不到,但可检测到β微管蛋白,死亡4d后,β微管蛋白也检测不到。结论肌动蛋白、微管蛋白的死后降解存在差异,其在肝脏组织保存时间的不同可作为死亡时间推断的参数。     

牙髓细胞DNA含量与死后经过时间的相关性

目的探讨死后不同环境温度下离体牙的牙髓细胞平均DNA含量变化与死后时间(PM I)的相关性。方法采用细胞图像分析系统(PIPS-2020),测定离体即刻至15d牙齿在低温环境(10~15℃)和高温(30~35℃)环境下牙髓细胞DNA含量变化值,并对其数据进行统计学分析。结果在不同的环境温度下,牙髓细胞DNA降解的速度有所不同,温度的升高有加速牙髓细胞DNA降解的趋势,且DNA降解存在一个平台期。低温组牙髓细胞平均DNA含量与PM I之间的相关系数r=0.953,相关指数R2=0.917;高温组的相关系数r=0.991,相关指数R2=0.971。结论牙髓细胞平均DNA含量与PM I之间具有高度相关性,测定牙髓细胞的DNA变化情况对推断3d(高温环境)或6d(低温环境)后的PM I有参考价值。     

单细胞凝胶电泳检测大鼠死后肝细胞核DNA降解

目的应用单细胞凝胶电泳技术(SCGE)检测大鼠死后肝细胞核DNA降解规律,分析与死亡时间的关系,为早期死亡时间的推断提供新的方法。方法在大鼠死后30h内,每隔3h取肝组织样本进行单细胞凝胶电泳,用共聚焦显微镜摄取彗星图像,应用彗星图像分析软件(IM I1.0)进行图像分析,并作统计学分析。结果死后大鼠的肝细胞在电泳图像上出现明显的彗星形拖尾,其尾长(TL)、尾矩(TM)在一定的时间范围内(0~18h)随死亡时间的延长而逐渐增大,二者均与死亡时间(PM I)呈现一定的相关回归关系。结论单细胞凝胶电泳技术可应用于早期死亡时间的推断。     

Evaluation of histologic changes of the skin in postmortem period

ABSTRACT: Determination of the time of death is an important consideration in forensic practice. Many methods have been attempted to accurately and systematically determine the postmortem interval (PMI). Histologic examination of the skin or appendages is one of the methods tried by few researchers. However, no attempt had been made to analyze the histologic changes in the skin and appendages simultaneously and to compare them with PMI. We sequentially studied the histologic changes of the skin and appendages in the early PMI. The results of the present study show that the skin undergoes progressive morphological changes in the postmortem period. The epidermis and the dermis appeared normal for 6 hours after death, and after this period, degenerative changes began. By 6 to 9 hours after death, degeneration began in the dermis, and by the end of 18 hours, the dermis began to disintegrate. The sweat glands appeared normal for approximately 3 to 4 hours. For 18 hours after death, the sebaceous glands and hair follicles appeared normal, and after this period, degeneration began.     

Estimation of postmortem interval from hypoxic inducible levels of vascular endothelial growth factor

Estimation of the postmortem interval (PMI) is one of the most important tasks in forensic medicine. Five autopsy organ tissues such as brain, lungs, heart, liver, and kidneys were taken at the time of forensic autopsy from 19 known PMI cases with a range of postmortem intervals ranging from 1 to 120 h (the mean was 25.81 h), and the time-course of vascular endothelial growth factor (VEGF) expression was measured. The human hepatoma-derived Hep 3B cell line was used as a control. The levels of VEGF increased linearly with the PMI up to 20 h in lung (r = 0.95 and in kidney (r = 0.89), and up to 15 h PMI in liver (r = 0.88). The VEGF levels fell after 24 h PMI, and then remained stable. In brain, the levels of VEGF started to increase after 24 h PMI and increased linearly with PMI up to 40 h in brain (r = 0.94) and then begin to fall. In heart, there was no clear correlation between the PMI and VEGF level. Some variations occurred in selected cases, such as the infant and asphyxial deaths. In conclusion, measurement of hypoxia-inducible levels of VEGF in various body organs appears to be a useful method of estimating the PMI up to 24 h in forensic medicine and pathophysiology. This method is also probably applicable in ischaemia in clinical and basic medicine.     

Estimation of postmortem interval using kinetic analysis of the third component of complement (C3) cleavage

To estimate postmortem interval (PMI), spontaneous cleavage of the third component of complement (C3) was studied in aged blood and cadaveric blood by crossed immunoelectrophoresis. Using the kinetics of C3 cleavage in vitro described as dC/dt = -kC, where C is the concentration of native C3 at time t and k is a first-order rate constant, Arrhenius' equation, and another equation which assumes a linear drop of body temperature after death, the percentages of C3 cleavage were calculated. There was a significant positive correlation between the calculated percentages and the measured percentages of up to 10% in cadaveric blood. We found that the comparison between the calculated percentage of C3 cleavage for each optional postmortem interval and the measured percentage of up to 10% in cadaveric blood leads to the estimation of PMI. This approach is one step towards the development of an accurate method for determining PMI based on C3 cleavage, that is, on a first-order reaction.     

Utilization of serum tryptase and immunoglobulin e assay in the postmortem diagnosis of anaphylaxis

The postmortem diagnosis of anaphylaxis is difficult. Serum concentrations of tryptase (a mast cell product released during anaphylaxis) have been used after death as an indicator of possible antemortem anaphylaxis. However, studies have indicated that tryptase may be elevated with increasing postmortem interval (PMI), or in nonanaphylactic deaths with significant atherosclerosis or chest trauma. Serum total IgE has been used by some to confirm anaphylaxis when tryptase is elevated. Serum levels of tryptase from 57 decedents with varying PMI, all dying of presumed nonanaphylactic causes, were determined. In cases with elevated levels (>11.4 ng/mL), an assay of total serum IgE was also performed. Both tryptase and IgE demonstrated significant elevations with increasing PMI. Decedents were categorized according to presence of cardiovascular disease, chest trauma, or both; many demonstrated elevation of 1 or both markers, without statistically significant differences between categories. Postulated mechanisms for nonanaphylactic elevations of these markers are reviewed. The possible utility of allergen-specific IgE or allergen panels is discussed.