Accurate Estimation Of Postmortem Interval Research Articles

Age estimation of Phormia regina pupae based on ATR-FTIR and chemometrics

Accurate postmortem interval estimation is vital in the investigation of homicides, suicides, and accidental deaths. It is key in narrowing suspect lists, improving crime-solving efficiency, and offering solace to bereaved families. The intra-puparial period, comprising about half of a fly’s developmental cycle, presents challenges for morphological age estimation. External changes are limited to color shifts and the appearance of respiratory horns on the puparium only within several hours after pupariation, while detailed internal development analysis often requires invasive methods like removing the puparium, which can be damaging. Additionally, these techniques usually depend on a forensic entomologist’s expertise, which lead to subjective biases. This study employed attenuated total reflection-fourier transform infrared spectroscopy, a rapid, non-destructive method for analyzing proteins, chitosan, and chitin in puparia. Data showed a consistent reduction in the concentration of the amide I band within the puparium during the intra-puparial development at five constant temperatures (19 °C, 22 °C, 25 °C, 28 °C and 31 °C). This trend in the spectral data effectively distinguishes pupae at various stages of intra-puparial development, facilitating precise age estimation, which is critical for the estimation of the minimum postmortem interval (PMImin). Finally, this work combined the total reflection-fourier transform infrared spectroscopy with chemometric analysis and successfully developed a partial least squares discriminant analysis model and a random forest model, with accuracies of 88 % and 81 %, respectively. These models enable the non-invasive age estimation of P. regina in its intra-puparial period, a stage traditionally difficult to assess morphologically, thus laying the groundwork for PMImin estimation using fly pupae.

MiR-122, miR-133a, and miR-206 as potential biomarkers for post-mortem interval estimation.

Accurate estimation of post-mortem interval (PMI) is crucial in forensic investigations. MicroRNAs (miRNAs or miRs) are small non-coding RNAs that remain relatively stable within the cell nucleus despite post-mortem changes. We assessed three target genes (miR-122, miR-133a, and miR-206) for PMI estimation using 72 healthy adult male BALB/c mice exposed to two different temperatures (4 and 21℃) at nine different time points over 10days. Initially, the stability of the two reference genes (RNU6B and 5 srRNA) was evaluated using gene stability analysis tools (Delta Ct, Best Keeper, and Genorm) to select the optimal reference gene. RNU6B was found to be the most stable endogenous control. Subsequently, the expression patterns of miR-122, miR-133a, and miR-206 were analyzed within a 10-day PMI period using the heart, skeletal muscle, liver, and brain tissues. At 4℃, miR-122 levels significantly decreased on days 8 and 10 in all tissues, with only the liver showing significant changes at 21℃. MiR-133a decreased over time in the heart, muscles, and brain, showing a dramatic decrease on days 8 and 10 in the heart and muscles at both temperatures. Although miR-206 levels decreased over time in muscles and liver at 4℃, these increased in the brain at 21℃, with no expression changes in other organs. In summary, miR-122, miR-133a, and miR-206 are potential PMI markers in heart and skeletal muscle tissues.

Evaluation of the effect of clonazepam and its metabolites on the life cycle of Megaselia scalaris (Loew) (Diptera: Phoridae)

Fly colonization patterns and development are crucial in estimating the post-mortem interval (PMI) of decomposing corpses. Understanding the potential effects of xenobiotics on species development in cadaveric entomofauna is essential for accurate PMI estimation, given their presence in decomposing bodies. Benzodiazepines, commonly prescribed for their anxiolytic, hypnotic, and muscle relaxant effects, are of forensic interest due to their potential for abuse, dependence, intoxication, and overdose-related deaths. This study aimed to explore the effect of clonazepam and its metabolites on Megaselia scalaris, a species commonly used to estimate PMI, the alteration of which could impact the accuracy of said estimation. The S9 biotransformation fraction, an in vitro model consisting of an array of metabolic enzymes, was used to generate phase I and II metabolites for evaluating their effect on M. scalaris development, representing an innovative approach to this type of study. Megaselia scalaris larvae were reared in synthetic growth media under controlled conditions. The study compared different groups: control, clonazepam, and clonazepam with S9 fraction. Larvae were measured daily to determine growth rate, and clonazepam concentrations were analyzed using HPLC-DAD. Results showed that larvae grown in media containing clonazepam or clonazepam with S9 fraction developed faster than control larvae, reaching their pupal stage earlier. Growth rates were also altered in treated groups. In conclusion, the presence of clonazepam and its metabolites accelerated the life cycle of M. scalaris, potentially impacting the accuracy of PMI estimation. These findings underscore the importance of considering xenobiotics in forensic entomological studies for precise post-mortem interval determination.

Decomposition in an extreme cold environment and associated microbiome-prediction model implications for the postmortem interval estimation.

The accurate estimation of postmortem interval (PMI), the time between death and discovery of the body, is crucial in forensic science investigations as it impacts legal outcomes. PMI estimation in extremely cold environments becomes susceptible to errors and misinterpretations, especially with prolonged PMIs. This study addresses the lack of data on decomposition in extreme cold by providing the first overview of decomposition in such settings. Moreover, it proposes the first postmortem microbiome prediction model for PMI estimation in cold environments, applicable even when the visual decomposition is halted. The experiment was conducted on animal models in the second-coldest region in the United States, Grand Forks, North Dakota, and covered 23 weeks, including the winter months with temperatures as low as -39°C. Random Forest analysis models were developed to estimate the PMI based either uniquely on 16s rRNA gene microbial data derived from nasal swabs or based on both microbial data and measurable environmental parameters such as snow depth and outdoor temperatures, on a total of 393 samples. Among the six developed models, the best performing one was the complex model based on both internal and external swabs. It achieved a Mean Absolute Error (MAE) of 1.36 weeks and an R2 value of 0.91. On the other hand, the worst performing model was the minimal one that relied solely on external swabs. It had an MAE of 2.89 weeks and an R2 of 0.73. Furthermore, among the six developed models, the commonly identified predictors across at least five out of six models included the following genera: Psychrobacter (ASV1925 and ASV1929), Carnobacterium (ASV2872) and Pseudomonas (ASV1863). The outcome of this research provides the first microbial model able to predict PMI with an accuracy of 9.52 days over a six-month period of extreme winter conditions.

Post-mortem interval estimation using miRNAs of road traffic accident cases: A forensic molecular approach

In forensic examination accurate estimation of post-mortem interval (PMI) is a challenging task, particularly in the advanced stages of decomposition. The existing methods (algor mortis, livor mortis, rigor mortis, putrefaction etc) used for estimating PMI rely on analyzing the physical, biochemical, and metabolic changes that occur in the corpse after death. While these methods have shown some level of effectiveness in estimating PMI during the early stages of decomposition, accurate estimation becomes increasingly challenging during the later stages of putrefaction when the body undergoes significant changes. Recently, microRNA (miRNA) profiling due to its relatively small size and stability has emerged as a promising tool in several areas of forensics. This study demonstrates the potential of miRNA for PMI estimation in advanced stages of death. In this study, miRNA-195, miRNA-206, and miRNA-378 were selected as target miRNAs and miRNA-1 as reference miRNA. Left ventricle tissue (5 g) of the heart from 20 forensic autopsies of traffic accident victims (18–32 years) were collected and processed. The samples were held at room temperature for eight different time intervals (12, 24, 48, 72, 96, 120, 168 and 196 h), and RNA was extracted from all the samples using Trizol-based RNA isolation protocol, followed by cDNA synthesis and amplification with commercially available specific miRNA probes in Real-Time PCR (RT-PCR), Ct was calculated. The result showed that miRNAs were associated with PMI. Over time, there were substantial changes in the Ct values of all three miRNAs, with significant reductions observed at 196 h compared to 12 h. miRNA-206 demonstrated significant changes at multiple time intervals, while miRNA-1 remained stable for up to 196 h and thus holds caas an endogenous marker. In conclusion, miRNA has the potential to serve as a valuable tool for estimating PMI, especially during the advanced stages of decomposition, when used in conjunction with established techniques. However, further validation of the study is required to obtain more accurate estimates of PMI.

A novel method for determining postmortem interval based on the metabolomics of multiple organs combined with ensemble learning techniques.

Determining postmortem interval (PMI) is one of the most challenging and essential endeavors in forensic science. Developments in PMI estimation can take advantage of machine learning techniques. Currently, applying an algorithm to obtain information on multiple organs and conducting joint analysis to accurately estimate PMI are still in the early stages. This study aimed to establish a multi-organ stacking model that estimates PMI by analyzing differential compounds of four organs in rats. In a total of 140 rats, skeletal muscle, liver, lung, and kidney tissue samples were collected at each time point after death. Ultra-performance liquid chromatography coupled with high-resolution mass spectrometry was used to determine the compound profiles of the samples. The original data were preprocessed using multivariate statistical analysis to determine discriminant compounds. In addition, three interrelated and increasingly complex patterns (single organ optimal model, single organ stacking model, multi-organ stacking model) were established to estimate PMI. The accuracy and generalized area under the receiver operating characteristic curve of the multi-organ stacking model were the highest at 93% and 0.96, respectively. Only 1 of the 14 external validation samples was misclassified by the multi-organ stacking model. The results demonstrate that the application of the multi-organ combination to the stacking algorithm is a potential forensic tool for the accurate estimation of PMI.

Estimating the Postmortem Interval of Carcasses in the Water Using the Carrion Insect, Brain Tissue RNA, Bacterial Biofilm, and Algae.

The accurate estimation of postmortem interval (PMI) is crucial in the investigation of homicide cases. Unlike carcasses on land, various biological and abiotic factors affect the decomposition of carcasses in water. In addition, the insect evidence (e.g., blow flies) that is commonly used to estimate the PMI are unavailable before the carcasses float on water. Therefore, it is difficult to estimate the PMI of a carcass in water. This study aimed to explore an effective way of estimating the PMI of a carcass in water. Carrion insects, brain tissue RNA, bacterial biofilm on the skin surface, and algae in water with PMI were studied using 45 rat carcasses in a small river. The results showed that carrion insects might not be suitable for the estimation of PMI of a carcass in water since they do not have a regular succession pattern as a carcass on land, and the flies only colonized six of the carcasses. The target genes (β-actin, GAPDH, and 18S) in the brain tissue were associated with the PMI in a time-dependent manner within 1 week after death. A polynomial regression analysis was used to assess the relationship between the gene expression profiles and PMI. The correlation coefficient R2 of each regression equation was ≥ 0.924. A third-generation sequencing analysis showed that the bacteria on the skin surface of the carcass and the algae in the water samples around the carcass had a regular succession pattern, where Cryptomonas and Placoneis incased and decreased, respectively, within first 9 days. The results of this study provide a promising way to use the brain tissue RNA, bacterial biofilm, and algae to estimate the PMI of a carcass in water.

Calliphorids as forensic indicator to facilitate PMI estimation: A case study from Chhattisgarh, India

ObjectivesCalliphorids especially blowflies are act as important forensic indicators as they are foremost visitors of the corpse and act as silent witness after the accomplishment of crime. MethodsIn present case study immature stages of blowflies utilized for PMI estimation. Postmortem Interval (PMI) of a highly putrefied male corpse in advanced stage of decomposition was estimated. Corpse was found under the culvert of Bijapur – Bhopalpatnam road, Village Modakpal, District Bijapur, State Chhattisgarh, India. PMI was determined with the help of Accumulated Degree Hours (ADH) method based on developmental period of third instar larvae of Blowfly Chrysomya megacephala (Fabricius). Tentative PMI of corpse is 5.5 days. Apart from Chrysomya megacephala immature stages as well as adults of Chrysomya rufifaces (Macquart) were also collected from deceased body. Entomological samples were sent for identification to the department of Zoology and Environmental Sciences, Punjabi University, Patiala, India. Results and conclusionsLarval stages were identified based on anterior and posterior spiracles and cephalophrangeal apparatus. Adults were identified based on their morphological characters. For accurate PMI estimation correct insect identification and meteorological data of crime scene are key parameters.

Research Progress on Developmental Biology of Sarcosaprophagous Insects.

Forensic entomology provides a feasible way to estimate postmortem interval (PMI), of which the growth and development of sarcosaprophagous insects is the most widely used indicator in forensic practice. Over the years, forensic entomologists have carried out a large number of studies on the development biology of sarcosaprophagous insects. This paper illustrates the main factors that affect the development of sarcosaprophagous insects, including temperature, humidity, light, food types and poisons. The development indicators of sarcosaprophagous insects were reviewed from the perspectives of morphology, differential gene expression and biochemical characteristics. It is emphasized that future research of development biology on sarcosaprophagous insects should fully absorb and integrate the methods of artificial intelligence and omics, and the research object also needs further expansion in order to establish a more objective and more accurate PMI estimation method.

Molecular Aspect of Post-mortem interval (PMI)

Post-mortem interval (PMI) is a major component of investigation in forensic science. It is one of the fundamental tasks for forensic pathologist when a body is found. According to criminal law point of view, a correct estimation of the PMI allows authentication of witness statements, thus restrict the number of suspects. Accurate PMI estimation is difficult because of intrinsic and extrinsic factors. Analysis of the biochemical changes in glucose and electrolytes for PMI estimation has made significant progress. Molecular ways in which measurable or quantifiable technique for degradation of nucleic acid molecule such as DNA and RNA, may be the good indicator for PMI. Several studies have tried to determine changes in molecular markers to provide more useful information for PMI. The studies demonstrated mixed results that showed the influence of ante and post-mortem factors on nucleic acid degradation. More studies would be required in order to standardize on human cases under standard parameters. Thus, molecular aspects of forensic involves this application of omicsin medical sciences to investigate cause of death and its process at the genetic basis and biological molecular level. Keywords: Post-mortem interval (PMI); Molecular biology; DNA and RNA quantification; Forensic Genetic identification.

Estimation of postmortem interval in myocardial stab wounds and firearm injuries: An immunohistochemical comparative study using C5b-9 and cardiac Troponin C

BackgroundEstimation of postmortem interval (PMI) is a critical component of forensic death investigations. C5b-9 and cardiac Troponin C (cTnC) have the potential as markers for myocardial damage and can be suitable markers for determination of PMI. The aim of current study was to estimate different postmortem intervals using C5b-9 and cTnC detected by immunohistochemical technique in stab wounds and firearm injuries of the heart. Materials and MethodsCardiac tissue samples from 70 forensic autopsy cadavers were obtained from XXXXXXX morgue, processed, for histopathological examination as well as immunohistochemical detection of C5b-9 and cTnC expression. The surface area of the positive C5b-9 and troponin C immune reactive cardiac tissue was measured morphometrically then the data were used to construct multiple regression equations for the estimation of PMI. ResultsHistopathological autolytic changes occurred in all groups and increased in intensity with the increase in the PMI in stab wound and firearm injury groups. These findings were supported by immunohistochemical morphometric analysis. Constructed equations to estimate PMI were highly accurate especially those combining both markers. ConclusionC5b-9 and cTnC can be considered reliable indicators of myocardial damage and can be used either separately or in combination for accurate estimation of PMI.

Difference analysis of accumulated degree-day samples in different regions of China

Background: Accumulated degree-days (ADD) refers to the temperature value and time within a certain period. More and more attention has been paid to the ADD in the study of postmortem interval (PMI) estimation. Aim and Objective: This study is to confirm whether ADD is applicable in China. Materials and Methods: We collected meteorological data of 10 different regions in China for 12 months, analyzed the distribution characteristics of ADD in different regions at different time periods, and tested the two ADD calculation methods (accumulated hourly temperature and accumulated daily average temperature), in an attempt to establish a more precise calculation method of ADD. Results: The results show that when the yearly or monthly effective temperature data is taken as the research object, the law of daily ADD mean value gradually decreases from south to north, and the average value of accumulated hourly temperature at each region is larger than the average value of accumulated daily average temperature (the difference was significant). In addition, in different periods of each day, ADD obtained at different regions is different, and the variation of its specific gravity also has a north-south difference. We take the daily average temperature as the independent variable and accumulated hourly temperature as the linear equation fitted by the dependent variable, showing a good linear relationship (0.992 ≤ R2 ≤ 0.999). At the same time, we also identify that extra caution should be exercised when using ADD in some special regions (such as Lhasa) or during the cold season of some regions. It may be unrealistic to attempt divide daily ADD into equal parts and accurately estimate PMI to a certain hour on the day of the crime. However, accurate estimation of PMI can be improved by dividing ADD on the day of the crime according to proportion of different periods and checking the time period of the final ADD value. Conclusion: At present, the study results on ADD need to be further developed. our study provides a preliminary research basis for the future establishment of an unified, simple, accurate, and suitable for the ADD model in China.

Effect of Environment Factors on Life Cycle of Forensic Entomology: A Review

Pests play an important ecological part in organic matter decomposition. As a natural means of survival,sarcosaprophagous fly usually prefers to locate and consume a food source such as a cadaver as a naturalmeans of survival. Sarcosaprohagous fly larvae are frequently encountered by judicial entomologistsduring post mortem investigations. The most relevant colonizers are the oldest individuals derived fromthe first eggs placed on the body. The stage of the oldest maggots provides the accurate estimate of postmortem interval. Judicial entomology is predictable in numerous countries as a serious tool for forensicinvestigations. Judicial entomology requires extensive information on the local pest population, is subjectto many environmental factors (temperature being one of the principle variables), and they need access tothe bodies. The maggot fly crawling on the dead bodies are broadly considered to be just another disgustingelement of decay and are not collected at the periods of autopsy. This paper reviews several methods of PMIassessment, this procedure comprises the aggregation of convenient information for the growth of the typesof pest at a variation of pertinent temperatures and contemplation of the extra living things and nonlivingthings aspects that can disturb evolving average.

A Comparative Study of Two Gel-Based Techniques to Detect the Relationship Between Post-Mortem Interval And Nuclear DNA Degradation In Different Tissues In Albino Rats

Background and objective: Postmortem interval (PMI) estimation is an important aim in forensic medicine. An accurate estimation of PMI helps to define the murder time and enable investigators in forensic field especially when they are collecting evidence that can reinforce or exclude the conducts of suspects in a crime. Some techniques were introduced to estimate postmortem interval with the aid of assessment of DNA fragmentation qualitatively and quantitatively. These include Agarose gel and single cell gel electrophoresis or comet assay. It is recommended to select the most appropriate method to overcome the troubles of postmortem DNA degradation. Methodology: 30 adult male Sprague Dawley albino rats were selected in the study. Animals were divided into 5 groups and were drowned at the beginning of the experiment. First group’s rats had sacrificed immediately after drowning, whilst the 2nd, 3rd, 4th and 5th groups were sacrificed at 6, 12, 24 and 48 hours postmortem respectively. The palatal mucosa and submandibular salivary glands were dissected and extracted for DNA studying and detection. The samples were processed through Agarose gel and single cell gel electrophoresis (comet assay) techniques to estimate the degree of DNA degradation. Results were analyzed statistically and Pearson correlation (r) was used to test the association between PMI & degradation of DNA. Level was considered significant at p value < 0.05. Results: Agarose gel technique revealed variation in DNA degradation ranging from no changes to severe changes with high correlation association between PMI and DNA in palatal mucosa samples but no correlation in samples of submandibular salivary glands. Comet assay results showed high correlation in all samples from both tissues between PMI and both of tail length and tail moment of the degraded DNA. Conclusion: Comet assay technique is a more reliable and dependable method in determination of early time of death as shown by the statistical analysis than did Agarose gel electrophoresis technique

A comparison of endogenous and exogenous RNA reference marker as relevant for accurate Post-Mortem Interval estimation

The Post Mortem-Interval (PMI), also known as time since death, is of relevance for forensic routine casework and serves primarily as the basis for the determination of the time that has passed since the time of death. The existing, “classical” approaches are characterised by certain limitations because they are predominantly based on morphological examinations.The present study deals with the assessment of two molecular messengerRNA-markers in different kinds post-mortem human specimens concerning their ability to use them for the estimation of the time of death. Moreover, a comparison between carefully selected endogenous and one exogenous reference marker for the normalisation of the gene expression data as relevant for accurate PMI estimation is drawn.The evaluation showed that the used approach is methodologically useful but on consideration of the achieved results it was only possible to determine slightly meaningful tendencies. The tested exogenous reference marker was not suitable for sufficient data normalisation whereas the endogenous reference markers showed a stable expression. However, it was not possible to recognise a specific expression level of the genes within a PMI group when endogenous reference markers were used.

Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectral prediction of postmortem interval from vitreous humor samples.

Evaluation of postmortem interval (PMI) is of paramount importance to guide criminal investigations, especially when witnesses are not found. However, accurate PMI estimation is a challenging task in the forensic community due to the limitations of existing methods. The study aims to investigate the potential of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy for predicting PMI based on vitreous humor (VH). VH samples were collected from 72 rabbits in the range of 0-48h postmortem at a 6-h interval. Their FTIR spectra were normalized by the extended multiplicative signal correction (RMSC) and divided into calibration and validation sets. After analysis of the absorption bands, the Bayesian ridge regression (BRR), support vector regression (SVR), and artificial neural network (ANN) methods were established by the calibration set using a 10-fold cross-validation that was further used to predict the PMI in the validation set. The validity of the models was assessed by a permutation test. The current study demonstrated that multiple macromolecules in the VH samples were reflected in a FTIR spectrum, and the spectral absorption bands at 1313 and 925cm-1 were highly correlated with PMI. The three models allowed generalization to the validation set due to similar R2 and errors between the calibration and validation tests. The highest accuracy with R2 = 0.983 and error = 2.018h was achieved by the ANN model in the validation test. The results suggest that ATR-FTIR spectroscopy may be useful for VH analysis in order to predict PMI in the future. Graphical abstract ᅟ.

HIF1α protein and mRNA expression as a new marker for post mortem interval estimation in human gingival tissue.

Estimating the post mortem interval (PMI) is still a crucial step in Forensic Pathology. Although several methods are available for assessing the PMI, a precise estimation is still quite unreliable and can be inaccurate. The present study aimed to investigate the immunohistochemical distribution and mRNA expression of hypoxia inducible factor (HIF‐1α) in post mortem gingival tissues to establish a correlation between the presence of HIF‐1α and the time since death, with the final goal of achieving a more accurate PMI estimation. Samples of gingival tissues were obtained from 10 cadavers at different PMIs (1–3 days, 4–5 days and 8–9 days), and were processed for immunohistochemistry and quantitative reverse transcription‐polymerase chain reaction. The results showed a time‐dependent correlation of HIF‐1α protein and its mRNA with different times since death, which suggests that HIF‐1α is a potential marker for PMI estimation. The results showed a high HIF‐1α protein signal that was mainly localized in the stratum basale of the oral mucosa in samples collected at a short PMI (1–3 days). It gradually decreased in samples collected at a medium PMI (4–5 days), but it was not detected in samples collected at a long PMI (8–9 days). These results are in agreement with the mRNA data. These data indicate an interesting potential utility of Forensic Anatomy‐based techniques, such as immunohistochemistry, as important complementary tools to be used in forensic investigations.

Updates In Estimating Postmortem Interval

Background: Estimation of postmortem interval is considered one of the most important issues in forensic medicine. It aids the police investigation and help to know the time of the crime and its relation to the assailant. It also important in some civil problems as inheritance. There are multiple methods that used for estimaton of PMI as: rate of cooling after death, detection of supravital reactions, rate of development of hypostasis, rigor mortis, life cycle of insect and the decomposition changes that occur after death. Also usage of body fluids as chemical method for estimation of time passed since death shows great advances. Recently application of DNA and RNA in this field has done aiming at more accurate estimation of PMI. Aim of the work: Introducing and establishing the basic knowledge about Postmortem Interval estimation and focusing on new approaches for postmortem interval estimation. Conclusion: PMI estimation is the time between time of death and time of identification of corpse. It has a role in forensic medicine specially in crimes. It helps to aid the police in their investigation and reduce the number of assailant. PMI estimation is still depend on early and late postmortem changes as algor mortis, rigor mortis, hypostasis and putrefaction. But recently there are new methods as detection of new biomarkers, using of microscopic changes that occur after death in multiple organs with success of these trials was noted and a correlation between them and PMI was found. DNA and RNA also participate in estimating time since death by detection the rate of degradation and its relation with PMI. Definition of postmortem interval (PMI): Postmortem interval (PMI) means the time passed since death. Estimation of PMI is done through information that depend on estimation of sets of time: Time A and Time B . Time A is the time when the decent was last known to be alive, while time B is the time when the decent was found dead. The time since death is presented certainly between these times (between death and examination of the dead body) based on different factors as algor mortis ,rigor mortis , postmortem lividity and decomposition (Prahlow, 2010). There are multiple early and late postmortem changes that may aid in PMI estimation

Estimation of Postmortem Intervals by Some Biochemical Changes and DNA Degradation in Rat Brain and Skeletal Muscle Tissues

Accurate estimation of postmortem interval (PMI) is one of the most important and difficult issues in forensic medicine. After death, the tissues undergo autolysis and biomacromolecules degrade. The relationship of extent of DNA damage and certain components of the oxidant/antioxidant balance in brain and femoral muscle tissues of rats killed by cervical dislocation or drowning, with the post-mortem intervals was investigated and examined by making a relation with the histopathological finding in brain tissue. The results showed that the oxidant/antioxidant balance in brain and femoral muscle tissue was shift insignificant favour of the oxidants at 24 hrs postmortem and lasted tell 96 hours post-mortem toward the oxidant. The percentage of DNA fragmentation was detected increased parallel to significant increase of oxidant level from zero to 96 hrs post-mortem. The histopathological alterations in brain and muscle tissues of drowned or cervical dislocation were found to be in full accordance with biochemical finding and DNA fragmentation. Our results suggest that biochemical analysis, DNA fragmentation as well as histopathological examination of brain and muscle tissues provide an accurate estimation of post-mortem intervals.

Studies on Time Duration of Life Stages of Chrysomya megacephala and Chrysomya rufifacies (Diptera: Calliphoridae) during Different Seasons

Accurate estimation of post mortem interval (PMI) can be crucial to the successful investigation of suspicious death. The forensic indicator blowflies are essential for accuracy in estimation of PMI. The Calliphoridae species Chrysomya megacephala and Chrysomya rufifacies were reared in laboratory condition for studying their time duration of different stages under the fluctuating temperature in three different seasons (i.e. rainy season, winter season and summer season). In laboratory, at the fluctuating temperature during rainy season, winter season and summer season, Chrysomya megacephala took 237 hours 47 minutes, 263 hours 51 minutes and 211 hours 13 minutes respectively. Whereas the Chrysomya rufifacies took 239 hours 14 minutes, 286 hours 02 minutes and 216 hours 26 minutes during rainy season, winter season and summer season respectively. This study shows that forensic investigators will have to take each of these variables into consideration from the development of insects in order to give a more accurate estimate of PMI.