Spectrophotometric Determination of Trimethylamine-nitrogen in Cadaver Tissues for the Estimation of Late Postmortem Interval:A Pilot Study

To study the relationship between the late postmortem interval （PMI） and trimethyl-amine-nitrogen （TMA-N） in postmortem tissues of cadaver, TMA-N in muscles, livers and kidneys of rats was measured at different postmortem intervals （PMI） by using a modified spectrophotometric method. The results indicated that the detection sensitivity of TMA-N was 1 mg/L, and there was a good linear correlation between the value of absorbance （A value） and TMA-N at the concentration of 1-10 mg/L （R2=0.9991）. Although TMA variation in muscles was different from that in inner organs during the time since death, TMA-N changes in cadaver tissues was positively correlated with PMI. During 2 to 7d since death, the best correlation between PMI and TMA-N concentration was found in muscles. With PMI as an independent variable, the cubic polynomial regression equation was y=-0.457x3 ＋6.519x2-24.574x＋27.207 （R2=0.969）. During 3 to 8 days since death, PMI was best correlated with TMA-N concentration in inner organs. With PMI as the independent variable, the cubic polynomial regression equation was y=0.509x3-9.153x2＋55.727x-95.819 （R2=0.953）. It was concluded that TMA-N in tissues could be used as a new estimator for late PMI. The method used in this study offered advantages such as accuracy, sensitivity, little samples required and wide PMI estimation.

Bioluminescent Assay of Microbial ATP in Postmortem Tissues for the Estimation of Postmortem Interval

To study the relationship between changes of microbial ATP in four kinds of murine tis-sues and the postmortem interval （PMI）, healthy SD rats were sacrificed and their muscles, livers, spleens and kidneys were sampled at different postmortem intervals. The concentration of microbial ATP was detected using bioluminescent assay and the data was statistically analyzed. The concentra-tion of microbial ATP in muscle increased with PMI time. The peak appeared at the 7th day after death, and at the 10th day, microbial ATP in muscle tissue increased again. In internal organs, the peaks of microbial ATP were observed at the 8th day after death and the level decreased during 8–10 d. The differences in microbial ATP concentration in liver, spleen and kidney were not statistically significant. During day 0 to day 9 after death, the correlation was best between PMI and microbial ATP in muscle. With PMI as the independent variable, the cubic polynomial regression equation was Y=0.02X3–0.166X2–0.666X＋13.412 （R2=0.989, P〈0.01）. In internal organs, the best correlation was found between PMI and microbial ATP during day 0 to day 10. With PMI as the independent variable, the cubic polynomial regression equation was Y=0.016X3–0.127X2–0.809X＋13.324 （R2=0.986, P〈0.01）. There existed high correlations between PMI and microbial ATP concentration in rat tissues. Since only a small amount of tissue was needed for the detection and the sample was not affected by self-decomposition, the method may extend the time range of PMI estimation.

Changes in ATP Levels in Rabbit Blood and Its Application for Estimation of the Postmortem Interval

Summary： Relationship between ATP changes of rabbit blood and postmortem interval （PMI） was studied. Twenty-four healthy rabbits were sacrificed and randomly divided into 3 groups with 8 rab- bits of each group. The bodies of three groups were placed in calorstat at temperature of 15℃, 25℃ and 35℃, respectively. The blood from the right ventricle was sampled through indwelling needle each 4 h until 72 h after death. ATP levels in the blood samples were measured by using ATP fluo- rescence rapid detection technique at different PMIs. Blood ATP levels slightly increased in the early stage after death and then constantly declined at all temperatures （15℃, 25℃, and 35℃）. Cubic polynomial regression equations with log[ATP] as dependent variable （y） and PMI as independent variable （x） at different temperatures and the optimal time period were established as followed： Under 15℃ and during 16-64 h after death, y=-3.027×10^-5x^3＋0.003x^2-0.096x-10.625 （Ra^2=0.992, P〈0.001）; under 25℃ and during 8-56 h after death, y=-2.921×10^-5x^3＋0.002x^2- 0.059x-11.186 （Ra^2=0.989, P〈0.001）; under 35℃ and during 4-36 h after death, y=-9.769×10^-5x^3＋ 0.005x^2 -0.117x-11.166 （Ra^2=0.991, P〈0.001）. The changes in ATP levels in blood collected from right ven- tricle of rabbit cadavers showed relatively stable and regular degradation within 72 h after death at different temperatures.

Image Analysis on Corneal Opacity:A Novel Method to Estimate Postmortem Interval in Rabbits

Corneal opacity is one of the most commonly used parameters for estimating postmortem interval （PMI）. This paper proposes a new method to study the relationship between changes of corneal opacity and PMI by processing and analyzing cornea images. Corneal regions were extracted from images of rabbits＇ eyes and described by color-based and texture-based features, which could represent the changes of cornea at different PMI. A KNN classifier was used to reveal the association of image features and PMI. The result of the classification showed that the new method was reliable and effective.

The Impact of Gender, Age and Tissues in vitro on Estimat- ing Postmortem Interval by FTIR Spectroscopy

To investigate the influence of such individual factors as gender,age and tissues in vitro to the postmortem interval(PMI) by the Fourier transform infrared(FTIR) spectrometer in animal experiments.SD rats were classified into male and female groups,different age groups(21-day,42-day and 63-day group),and tissues in vitro and in vivo groups.The rats were sacrificed by cervical dislocation,whose bodies were kept in a controlled environmental chamber set at(20±2) ℃ and 50% humidity.The liver,kidney,spleen,myocardium,brain,lung and skeletal muscle tissues were collected for measurement from time zero to 48 h postmortem.With the change of PMI,no obvious changes were found in the main FTIR absorbance peaks and their ratios at different time points.All the experimental groups showed no significant changes when compared with the controls.The gender,age and tissues in vitro were not found to be contributing factors in the estimation of PMI via FTIR spectroscopy.

人工智能技术驱动的法医病理时间类问题解决策略

在法医病理学领域,死亡时间、损伤时间、血痕遗留时间及血栓形成时间等时间类问题与案发时间及死因分析直接相关,在案件侦破、责任划分和定罪量刑等司法环节中起着关键作用。随着人工智能(artificial intelligence,AI)技术的发展,各行业对数据分析需求持续增加,以模拟人脑为代表的机器学习技术已经应用于医学研究的多个领域,为法医病理时间类问题的解决提供了新的方法和思路。通过对近年涌现出的一系列应用AI技术解决法医病理时间类问题的相关文献进行综述,以期为复杂鉴定问题研究提供帮助和激发新思考,为司法实践活动提供更为科学、客观的鉴定证据。

溺亡后肠道菌群变化综述

对死后间隔时间(postmortem interval,PMI)的推断,是法医界最大的难题之一,从传统的根据尸体现象推断PMI到如今利用硅藻检验、影像学、分子生物学及人工智能等众多高新技术,极大地提高了PMI判断的准确性。人体死亡后,肠道菌群将发生剧烈变化,因此,分析肠道菌群的变化特点可以为法医鉴定提供新思路。通过肠道微生物分析,建立PMI与肠道菌群之间的关系,从而提高PMI的精确性,极大地拓展了肠道菌群的研究范畴。文章就溺亡尸体肠道菌群的时序性变化进行了简要综述,旨在探讨肠道菌群在法医实践中推断死亡时间的应用现状及应用前景。

应用法医微生物学推断死亡时间研究进展

死亡时间推断一直是法医学领域的重点和难点问题。研究发现尸体微生物群落演替规律与死亡时间之间呈现高度相关,其可为死亡时间推断提供新方法。近年来,国内外学者利用法医微生物学理论与方法对存在于不同环境中的尸体死亡时间推断进行了大量研究,丰富了死亡时间推断方法,提高了死亡时间推断的准确性。本文就暴露、埋藏和水中三种环境下尸体菌群演替规律的异同进展作简要综述,以期探讨不同环境下利用法医微生物学推断死亡时间的研究现状、所面临的问题及应用前景。

利用微生物菌群演化及免疫系统的影响辅助推算死后时间

准确推算非正常死亡间隔时间(PMI),是法医需要面对的首要问题之一。基于分析死者体内特定微生物标志物的演变规律来量化死亡时间,具有科学性和精确性。同时,免疫系统与体内微生物群结构相互作用。为准确推算PMI提供了新的研究方向。采用DNA二代测序技术,深入研究描述微生物群落动态变化,为推算PMI提供了重要依据。本文通过用Illumina MiSeq测序法分析高变区域的短片段、用Nanopore (MinION)测序法进行全测序的特点,对比了16S核糖体RNA(16S ribosomal RNA)扩增测序实验,并详细梳理了建立死亡时间模型的历程,肯定了AI技术的辅助推动作用。本文还建议更多关注微生物群与免疫系统的关系,肯定了微生物学在法医科学领域的重要价值。

Inferring the Postmortem Interval of Rat Cadaver after Boiling Water Treatment Based on Microbial Community Succession

Background:In forensic investigations,accurate estimation of the postmortem interval(PMI)is an important task,but also an ongoing challenge.Especially in cases where the cadaver has been specially treated,for example,by boiling,the determination of PMI becomes extremely difficult.Previous studies have shown that the succession of the microbial community after decomposition of the cadaver can be used to infer PMI.However,the feasibility of determining the PMI of boiled cadavers has not yet been demonstrated.Aims and Objectives:The main objective of this study was to test whether we can infer PMI of boiled cadavers based on the succession of microbial communities.Materials and Methods:SD rats were killed by cervical dislocation.Subsequently,the rat cadavers were divided into the case(boiled cadavers)and control(unboiled cadavers)groups.Rectal samples were collected from the rats for 45 days and at nine time points.High-throughput sequencing of the 16S rRNA gene was performed to characterize the microbial community in the rectum.Results:The results showed that the composition and relative abundance of bacterial communities at the phylum level were significantly different between the case and control groups.The alpha diversity of the microbial community showed a decreasing trend with the decomposition process.Principal coordinate analysis showed that the case and control groups had obvious patterns along the succession of microbial communities.The rectal microbial communities showed a significant linear trend in the time course of decomposition.A random forest model was used to infer PMI.The goodness-of-fit(R2)of the model was 68.00%and 84.00%,and the mean absolute errors were 2.05 and 1.48 days within 45 days of decomposition for the case and control groups,respectively.Conclusions:Our results suggest that microbial community succession could be a potential method to infer PMI of boiled cadavers.

DNA degradation within mouse brain and dental pulp cells 72 hours postmortem

In this study, we sought to elucidate the process of DNA degradation in brain and dental pulp cells of mice, within postmortem 0-72 hours, by using the single cell gel electrophoresis assay and professional comet image analysis and processing techniques. The frequency of comet-like cells, the percentage of tail DNA, tail length, tail moment, Olive moment and tail area increased in tandem with increasing postmortem interval. In contrast, the head radius, the percentage of head DNA and head area showed a decreasing trend. Linear regression analysis revealed a high correlation between these parameters and the postmortem interval. The findings suggest that the single cell gel electrophoresis assay is a quick and sensitive method to detect DNA degradation in brain and dental pulp cells, providing an objective and accurate new way to estimate postmortem interval.

Time-Dependent FTIR Spectral Changes in Rats of Massive Hemorrhage Death during the Later Postmortem Period

The aim of the current study was to investigate the spectra in the different organs of the rats which died of massive hemorrhage;to explore their spectral changes 15 days postmortem and the best mathematical model with different band absorption ratio changes to postmortem interval(PMI);and to compare the spectral changes of different temperature.Thirty male Sprague-Dawley rats were sacrificed by cutting abdominal aorta,and the cadavers were divided equally and kept at 4 ℃,20 ℃ and 30 ℃ in the control chamber.From the same rat,seven different organs were sampled at intervals of 1-15 days postmortem,and then measured by Fourier transfom infrared(FTIR) spectrometer.Six mathematical model functions were explored.The absorbance of bands and band absorbance ratios of absorption peak in each organ showed a time-dependent increase or decrease,most band absorbance ratios remaining stable for 7-15 days postmortem.Cubic model functions of the various bands absorbance ratios against PMI showed a stronger related coefficient.The absorbance bands with obvious changes at 20 ℃ showed stabilized tendencies at 4 ℃ and significant changes at 30 ℃ within 15 days postmortem.In addition,FTIR spectroscopy revealed a time-dependent metabolic process,with potential of being used to estimate PMI during 7 days postmortem,which merits further investigation.

蛋白质芯片检测技术结合多维统计方法推断死亡时间

目的利用蛋白质芯片检测技术结合多维统计方法分析骨骼肌组织的蛋白质变化,进行死亡时间推断。方法大鼠颈椎脱臼处死后置于16℃环境中,提取死后不同时间点(0 d、1 d、2 d、3 d、4 d、5 d、6 d、7 d、8 d和9 d)骨骼肌的水溶性蛋白质,获取相对分子质量为14000~230000的蛋白质表达谱数据,采用主成分分析(principal component analysis,PCA)和正交偏最小二乘(orthogonal partial least squares,OPLS)进行数据分析,构建Fisher判别模型及反向传播(back propagation,BP)神经网络模型对大鼠死亡时间进行分类预测。另外收集不同死亡时间的人体骨骼肌蛋白质表达谱数据,通过热图和聚类分析观测其与死亡时间之间的关系。结果大鼠骨骼肌蛋白质谱峰随死亡时间呈一定的时序性变化。PCA结合OPLS判别分析结果显示,除死后6 d、7 d和8 d外,各死亡时间组间差异有统计学意义(P<0.05);经Fisher判别分析,模型内部交叉验证准确率为71.4%,外部验证准确率为66.7%;BP神经网络模型分类预测结果显示,模型内部交叉验证准确率为98.2%,外部验证准确率为95.8%。经聚类分析,人体骨骼肌蛋白质表达在死后4 d与死后25 h内差异有统计学意义。结论蛋白质芯片检测技术可快速、准确、高重复性地获取死后不同时间点大鼠和人体骨骼肌相对分子质量为14000~230000的水溶性蛋白质表达谱,建立基于多维统计方法的多种死亡时间推断模型,有望为死亡时间推断提供新的思路和方法。

微生物群落演替在死亡时间推断中的研究进展

死亡时间推断是法医学实践中的重点和难点,国内外法医学者一直在探寻客观、可量化和准确的死亡时间推断方法。随着高通量测序技术和人工智能技术的发展与结合,根据死后尸体相关的微生物群落演替规律建立死亡时间推断模型,成为法医学领域的研究热点。本文就利用高通量测序技术探究微生物群落在死亡时间推断中的技术方法、研究应用及影响因素等方面进行综述,为利用微生物群落推断死亡时间的相关研究提供参考。

基于眼组织结构的死亡时间推断研究进展

死亡时间(postmortem interval,PMI)推断是法医病理学研究的重点与热点问题。近年来,国内外学者利用眼组织推断PMI取得了一定进展,机体死后眼角膜、房水、虹膜、晶状体、玻璃体液、视网膜等改变均呈现与PMI高度相关的时序性变化规律。本文基于眼组织不同结构死后形态学、生物化学、分子学、遗传物质改变等方面,对PMI推断研究进展进行了综述,对存在的问题及发展趋势进行探讨。

电化学方法在法医学中的研究进展

电化学方法是基于电流导致的化学变化以及通过化学反应产生的电学性质变化的分析方法,在环境检测、食品分析、医学检验等诸多领域已广泛应用。近年来,随着电化学技术的迅速发展,其相关研究也拓展至法医学领域。该文概述了电化学方法在死亡时间推断、指纹显现和法医毒物分析等法医学领域中的研究进展,分析了电化学方法在应用中存在的问题,并对其应用前景提出未来展望,以期为相关科学研究和实践提供新思路。

Research progress in the estimation of the postmortem interval by Chinese forensic scholars

The determination of time since death or the postmortem interval(PMI)is one of the most important and frequently asked questions in forensic medicine.Medicolegal scholars and forensic pathologists around the world have studied the estimation of PMI extensively in the past,and many novel methods and advanced technologies have now been applied in the field.For several centuries,Chinese forensic examiners have also worked on the estimation of the PMI,and there are a large number of excellent studies published in Chinese rather than in English,and these are not easily accessible or known internationally.Therefore we have conducted a review of relevant studies published by Chinese forensic scholars in the last few decades.The scope of this review is to provide a concise summary of the current progress in the estimation of PMI by Chinese forensic researchers using molecular biology,spectroscopic technology,entomological methods,energy changes,thanatochemistry and other methods.

Determination of Electrical Conductivity of Cadaver Skeletal Muscle: A Promising Method for the Estimation of Late Postmortem Interval

The electrical conductivity(EC)of extracted muscle fluid has been extensively used to evaluate meat freshness and shelf life in the field of food sanitation for decades.The opposite of freshness is the corruption that increases with time.Based on the freshness/corruption principle,we investigated the relationship between long postmortem intervals(PMIs)and EC in cadaver skeletal muscle.EC values of extracted fluid from rat muscles were measured at different PMIs for 10 days.The results indicate that there was a significant correlation between PMI and EC,and the data fit well to the cubic polynomial regression equation y=‑0.01x3+0.264x2‑13.657x+1769.148(R2=0.925).In addition,the EC of different dilutions of these muscle extracts showed strict quadratic correlation(R2=1)with the dilution ratios,suggesting that EC can be measured with very small quantities of muscle sample.Our study suggests that determination of the EC of cadaver skeletal muscle extracts may be a useful method for estimating long PMIs.

Determining the Electrical Conductivity of Rat Cadaveric Liver,Spleen,and Kidney to Estimate Early Postmortem Interval

Previous research has found that electrical conductivity(EC),an important index to predict meat freshness and shelflife,is very promising for estimating the late postmortem interval(PMI).However,whether it has potential use in the early PMI has not been fully studied yet.To test this possibility in the present study,EC of three internal organs of rat liver,spleen,and kidney were determined within 24 postmortem hows,and then,EC changes at different PMIs were carefully analyzed.The overall results showed that EC of liver and spleen increased significantly with PMI while EC of kidney had minor changes during the same period.Specifically,significant linear positive correlations between EC of liver and spleen and PMI were found and the coefficients of their regression functions were R^(2)=0.98 and R^(2)=0.95,respectively.It can be concluded that determination of EC in certain internal organs such as liver and spleen may be a potential tool in the early PMI estimation.However,more researches on its influencing factors are needed to facilitate its final use in practice.

Estimation of Postmortem Interval Using the Radiological Techniques,Computed Tomography:A Pilot Study

Estimation of postmortem interval(PMI)has been an important and difficult subject in the forensic study.It is a primary task of forensic work,and it can help guide the work in field investigation.With the development of computed tomography(CT)technology,CT imaging techniques are now being more frequently applied to the field of forensic medicine.This study used CT imaging techniques to observe area changes in different tissues and organs of rabbits after death and the changing pattern of the average CT values in the organs.The study analyzed the relationship between the CT values of different organs and PMI with the imaging software Max Viewer and obtained multiparameter nonlinear regression equation of the different organs,and the study provided an objective and accurate method and reference information for the estimation of PMI in the forensic medicine.In forensic science,PMI refers to the time interval between the discovery or inspection of corpse and the time of death.CT,magnetic resonance imaging,and other imaging techniques have become important means of clinical examinations over the years.Although some scholars in our country have used modem radiological techniques in various fields of forensic science,such as estimation of injury time,personal identification of bodies,analysis of the cause of death,determination of the causes of injury,and identification of the foreign substances of bodies,there are only a few studies on the estimation of time of death.We detected the process of subtle changes in adult rabbits after death,the shape and size of tissues and organs,and the relationship between adjacent organs in three-dimensional space in an efiort to develop new method for the estimation of PMI.The bodies of the dead rabbits were stored at 20℃ room temperature,sealed condition,and prevented exposure to flesh flies.The dead rabbits were randomly divided into comparison group and experimental group.The whole-body CT scans were performed on the experimental group of rabbits at different PMIs.NeuViz dual-slice spiral CT scanner(made by Neusoft Medical in China,2 mm×10 mm high-speed rare earth ceramic detector)is a 360°scan that could obtain two images,capable of providing a wide range of high-speed continuous spiral scan.Max Viewer(Version:1.0.0131,Neusoft,Shenyang,China)is a CT image viewing software developed by Neusoft Medical.The software can be used to view and process images in various common methods and to measure a number of parameters,such as length,area,angle,and CT values.Statistical analysis was performed using SPSS1 Statistics 19.0(SPSS,Inc.,Chicago,IL,USA).AP<0.05 was considered statistically significant.We obtained the binomial regression equation of the CT values and the related coefficient(R^(2)).In the future,we suggests that comprehensive analyses of various indicators of different organs could establish a diversified pattern to remedy the deficiencies and make the study of PMI estimation more scientific and enhance the operability.