Death Time Estimation Research Articles

An assessment of the Henssge method for forensic death time estimation in the early post-mortem interval.

Time-since-death (TSD) diagnostics are crucial in forensic medical casework. The compound method by Henssge and Madea, which combines temperature and non-temperature-based techniques, is widely used to estimate TSD. This study aims to validate the predictive ability of this method in a cohort of 76 deceased individuals with known times of death (TOD). A convenience sample of 76 deceased individuals was examined at the Institute of Legal Medicine, University Medical Center Hamburg-Eppendorf. The study included individuals who died at the hospital and those with sudden death in public. Exclusion criteria included age under 18, known infection or sepsis, polytrauma, bleeding, and hyperthermia. The TSD interval was calculated using the Deathtime software. The overall agreement between the actual TOD and the 95% prediction interval for the TSD was 36.8% (95% CI: 26.1 to 48.7). Warm-stored corpses showed a higher agreement (61.9% [95% CI: 38.4 to 81.9]) compared to cold-stored corpses (27.3% [95% CI: 16.1 to 41.0]). Factors such as body mass index (BMI) and body surface area (BSA) were found to influence the odds of agreement. Assuming a plausible range of ambient temperatures between death and admission improved the agreement in cold-stored cases. The study found low to moderate agreement between the actual TOD and the 95% prediction interval using the Henssge method. Incorporating BMI and BSA could improve the predictive accuracy of TSD estimations. Further research with larger sample sizes and external validation is recommended to refine the model.

Time of Death Estimation: The Role of Hermetia illucens in bones in the Savannah of Goiás

Time of Death Estimation: The Role of Hermetia illucens in bones in the Savannah of Goiás

Examination of postmortem changes in the lungs, trachea, and bronchi in a rat model imaged with small-animal computed tomography.

As less autopsies are performed, the need for postmortem computed tomography (PMCT) as an alternative is increasing. It is important to know how postmortem changes over time are reflected on CT, in order to improve the diagnostic capability of PMCT and replace forensic pathology evaluations such as time of death estimation. In this study, we examined temporal changes on postmortem chest CT images of a rat model. After acquiring antemortem images under isoflurane inhalation anesthesia, the rats were euthanized with a rapid intravenous injection of anesthetics. From immediately after death to 48 hours postmortem, chest images were acquired using small-animal CT. The 3D images were then evaluated on a workstation to measure the antemortem and postmortem air content in the lungs, trachea, and bronchi over time. The air content in the lungs decreased, but the air content of the trachea and bronchi temporarily increased 1-12 hours postmortem, then decreased at 48 hours postmortem. Therefore, the measurement of trachea and bronchi volumes on PMCT could be an objective way to estimate the time of death. While the air content of the lungs decreased, the volume of the trachea and bronchi temporarily increased after death, indicating the potential to use such measurements to estimate time of death.

Quality measures for fully automatic CT histogram-based fat estimation on a corpse sample

In a previous article a new algorithm for fully automatic ‘CT histogram based Fat Estimation and quasi-Segmentation’ (CFES) was validated on synthetic data, on a special CT phantom, and tested on one corpse. Usage of said data in FE-modelling for temperature-based death time estimation is the investigation’s number one long-term goal. The article presents CFES’s results on a human corpse sample of size R = 32, evaluating three different performance measures: the τ-value, measuring the ability to differentiate fat from muscle, the anatomical fat-muscle misclassification rate D, and the weighted distance S between the empirical and the theoretical grey-scale value histogram. CFES-performance on the sample was: D = 3.6% for weight exponent α = 1, slightly higher for α ≥ 2 and much higher for α ≤ 0. Investigating τ, S and D on the sample revealed some unexpected results: While large values of τ imply small D-values, rising S implies falling D and there is a positive linear relationship between τ and S. The latter two findings seem to be counter-intuitive. Our Monte Carlo analysis detected a general umbrella type relation between τ and S, which seems to stem from a pivotal problem in fitting Normal mixture distributions.

Core body temperatures during final stages of life—an evaluation of data from in-hospital decedents

Temperature-based methods are widely accepted as the gold standard for death time estimation. In the absence of any other information, the nomogram method generally assumes that a person died with a core body temperature of approximately 37.2 °C. Nevertheless, several external and internal factors may alter the body temperature during agony. A retrospective medical record analysis was carried out on in-hospital death cases from two consecutive years of surgical intensive care units to determine the effects of factors influencing the core body temperature at the point of death. Data from 103 case files were included in the statistical data evaluation. The body temperature fluctuated between and within individuals over time. No clear correlation to certain death groups was observed. Even primary cardiac deaths showed broad intervals of temperatures at the point of death. Men seem to die with higher body temperatures than women. The presented data highlight potential biases for death time estimations when generally assuming a core body temperature of 37.2 °C. In conclusion, the estimation of the time of death should include various methods, including a non-temperature-dependent method. Any uncertainties regarding the body temperature at point of death need to be resolved (e.g. by identifying fever constellations) and elucidated if elimination is not possible.

Prism (II): 127 cooling dummy experiments

The Prism method for temperature based time since death estimation has been demonstrated as a proof of principle in 2021. Now it was validated experimentally. 10 cooling dummies (physical weights from 5.9 kg to 26.9 kg) were fabricated and fitted with temperature probes. A total of 127 dummy cooling experiments were conducted (total cooling time 2082 h, average cooling time 24.6 h) for both regular and elevated starting temperatures, covering ambient temperatures between − 14.0 °C and + 24.0 °C and for different cooling conditions. Cooling data was recorded, then cropped, smoothed, fed into the Prism workflow, and analyzed using dedicated scripts written in the Python programming language. Calculations did not take any additional information into account. No correction factors were needed. General Prism cooling weight curves were confirmed (false ambient temperature and elevated rectal temperature at the time of death). Sub-zero ambient temperature generated unexpectedly large cooling weights. Time since death estimation errors were − 0.29 h ± 5.24 h (whole course of cooling, all experiments) and were typically smaller in earlier stages of cooling. Prism performed relatively well, where conventional temperature based death time estimation struggles. In the future it may potentially be adapted to known conditions. Our results indicate that Prism’s cooling weight might serve as a highly individual, case-based data-driven umbrella parameter, replacing (subjectively) estimated parameters.

The impact of anatomy models on time of death estimation

The impact of anatomy models on time of death estimation

Prism – A novel approach to dead body cooling and its parameters

In temperature based death time estimation, the mathematical description by Marshall and Hoare is combined with the parameters defined and additional correction factors introduced by Henssge in the Nomogram method (summarized as MHH). Parameters and correction factors however leave room for subjectivity and disagreement. Elevation of rectal temperature at the time of death has been acknowledged as problematic for death time estimation in several studies, but has neither been solved nor systematically integrated into death time estimation methodology. Ambient temperature, when non-constant and/or unknown, may introduce additional errors. Further problems may arise if the fundamental relationship between torso dimensions and total body weight is not comparable to Henssge’s dummy cooling model. In this study we present a novel methodological approach to temperature based death time estimation, in which relevant parameters for calculations may be evaluated, corrected and generated using brute-force calculations. Consistency of death time over the course of cooling is used as brute-force target. The calculations produce momentary cooling weights, which are graphed over time. Cooling weight graphs can be analyzed to draw conclusions related to different parameters. The method was used on artificial ideal cooling data which was generated according to MHH for known parameters. Correctness of assumed parameters was confirmed by a linear horizontal path of the cooling weight graph. However, controlled false value input resulted in characteristic graph variations. Elevated rectal temperature at the time of death was detectable from the curve shape until hours after cooling below regular temperature at death. False high and false low ambient temperature produced positive and negative curve slopes. Overall, the method acts much like a prism which breaks up light into its elemental colors. It holds potential for application both in scientific settings and practical case work.

Analytical Strategy for MS-Based Thanatochemistry to Estimate Postmortem Interval.

An analytical strategy for a matrix-assisted laser desorption mass spectrometry-based untargeted metabolomic study on vitreous humor (VH) was developed, looking for statistically significant parameters correlated to death time estimation. Five incubation stages of VH, 0, 24, 48, 72, and 96 h, at physiological pH and controlled temperature, were adopted to monitor time-dependent changes and correlate them with the postmortem interval (PMI). Using two multivariate statistical approaches, principal component regression (PCR) and partial least squares regression (PLSR), the PMI was assessed, considering the m/z values from mass spectra and the incubation time (ISt) as predictors. An independent validation set was used to evaluate the predictive capability of the models through the coefficient of determination (R2) and the root-mean-square error (RMSE). Different pre-treatments were applied to the raw mass spectra, and their performance in assessing PMI was evaluated. Based on the best outcomes in terms of both R2 and RMSE, multiplicative scatter correction combined with a logarithmic transformation was chosen. The results of PCR and PLSR based on the selected pre-treatment are encouraging because validation R2 is about 0.95 for both models. Moreover, the prediction error is 6 h for both models, when PMI is lower than 1 day. Although these results are obtained by the uncritical application of the models, they are comparable to or even better than those reported in the literature. Notwithstanding, we consider that many in situ influences, such as passive diffusion, functional loss of tissues, and advanced autolytic processes, could not get captured in vitro. However, the developed approach was optimized using VH samples and overcomes the limitations of the vast majority of methods that require validation for serum and/or urine samples.

Death time estimation of water heritages in Gonabad Plain, Iran

A Qanat is a hydraulic structure for the extraction of the groundwater using only gravity force without need to apply external force through pumping. The deepest and oldest Qanats in the world are located in the Gonabad Plain in the Razavi Khorasan Province, east of Iran. Qanats have been the most important approach for groundwater extraction and survive in arid region such as the study area for thousands of years, but they are disappearing because of climate and human factors. In the present research, descending trends of flow rate of four historical Qanats (i.e., Rahn, Baidokht, Kheshuie and Qasabeh) of the Gonabad Plain have been studied and analyzed using discharge values of the Qanats over the last 33 years. Effective factors on discharge values of these Qanats have also been discussed. The analysis indicated that the amount of precipitation in the study area and its mountains has decreased significantly since 2000. Moreover, because of drinking demand and traditional agriculture consumptions, the amount of annual groundwater extraction through deep wells has increased since 1960 and its amount reached 12 million cubic meters. As the groundwater drawdown increases, the water-bearing zone of the Qanats will decrease and the Qanats will dry gradually. The annual groundwater level drawdown in the Gonabad Plain is 0.1 m per year. The discharges of the different Qanats in the Gonabad Plain have been dropped from 38 to 9 L/s during the last 33 years. The results indicated that the discharge reduction of the Qanats is 4–14 L/s due to one meter groundwater level drawdown. As the groundwater drawdown continues with the current rate in the Gonabad Plain, these valuable water heritages will perish over 9–157 next years for the aforementioned Qanats. To prevent the destruction of the Qanats, it is suggested to reduce 7.2 MCM of groundwater extracted through wells by optimal use of water and prevent the development of agriculture and industries that need water in the Gonabad Plain.

Estimation of time since death after a post-mortem change in ambient temperature: Evaluation of a back-calculation approach

The temperature-based “Henssge method” is widely applied for death time estimation. For cases with a sudden post-mortem (pm) change in ambient temperature (e.g., by bringing the deceased into a cooling chamber), a mathematical approach has already been proposed [1] that enables estimation of the time of death by back-calculation of body temperature.This approach was evaluated under clinically controlled conditions. Twenty-five individuals who died in a neurosurgical intensive care unit were brought to cooling storage after approximately 3 h pm. Body temperature was repeatedly measured on the ward and in cooling storage over a period of 9 h pm.Back-calculation of body temperature was carried out on the basis of the proposed mathematical approach for cases with pm changes in ambient temperature; the results were compared to the known body temperatures.In many cases, the back-calculated and true body temperatures differed widely. Bodies regularly cooled down slower after being brought into cooling storage than the back-calculations indicated. The sudden change in ambient temperature could only be addressed roughly by the proposed method of back-calculation.In conclusion, the evaluated approach for addressing pm changes in ambient temperature should only be applied with great caution.

Modern possibilities and prospects of research of fluids and environments of the human organism for the time of death estimation

The issue of determining the time of death has always been relevant among forensic doctors, since determining the exact moment of death allows the investigating authorities to clarify the circumstances of death and identify those, who are involved in crime.Objective –to analyze the methods used in practice in the regional bureaus of forensic medicine of Ukraine and abroad in order to identify their effectiveness for the establishment of time since death by studying biological fluids and environments of the human body, as well as to identify their problems for further development of new methods or modernization of existing ones.In recent decades forensic scientists have developed a number of different methods to determine the post-mortem interval. The possibility of studying biological fluids and environments of the human body, such as cerebrospinal fluid, vitreous body, synovial fluid, is especially relevant because they are isolated from the environment and the influence of external factors. Biochemical methods are mainly used for their research. For vitreous body one of the most studied and used indicators in practice by forensic experts is potassium. The dynamics of changes in its concentration with increasing time after death is also characteristic of other biological fluids of the human body.Conclusion. There is an active search for new methods that could simplify the study of biological fluids and human media to determine the time of death, as well as improve their accuracy. Such methods may be laser autofluorescence and multiparameter laser tomography.

Computationally approximated solution for the equation for Henssge\u2019s time of death estimation

BackgroundTime of death estimation in humans for the benefit of forensic medicine has been successfully approached by Henssge, who modelled body cooling based on measurements of Marshall and Hoare. Thereby, body and ambient temperatures are measured at the death scene to estimate a time of death based on a number of assumptions, such as initial body temperature and stable ambient temperature. While so far, practical use of the method resorted to paper print outs or copies of a nomogram using a ruler, increasingly, users are interested in computer or mobile device applications. We developed a computational solution that has been available online as a web accessible PHP program since 2005. From that, we have received numerous requests not so much to detail our code but to explain how to efficiently approximate the solution to the Henssge equation.MethodsTo solve Henssge’s double exponential equation that models physical cooling of a body, it is sufficient to determine a difference term of the equation that will be close to zero for the correct time of death using a discrete set of all sensible possible solutions given that the modelled time frame has practical upper limits. Best post-mortem interval approximation yields minimal difference between equation termsResultsThe solution is approximated by solving the equation term difference for a discrete set of all possible time of death intervals that are sensibly found, and by then determining the particular time of death where equation term difference is minimal.ConclusionsThe advantage of a computational model over the nomogram is that the user is also able to model hypothermia and hyperthermia. While mathematically impossible to solve in a straightforward way, solutions to the Henssge equation can be approximated computationally.

Temperature-based death time estimation in near equilibrium: Asymptotic confidence interval estimation

Temperature based death time estimation (TDE) is severely limited in situations where body core temperature has almost decreased to ambient temperature. The TDE method of Marshall/Hoare and Henßge (MHH) defines a lower bound TK for body core temperature below which the time p.m. should be stated to be >10h only.A recent study (Potente et al., 2017 [10]) established a new method, called variance-bias-tradeoff (VBT) complementing MHH in constructing a right-side-half-infinite 97.5%-confidence interval for such ‘near equilibrium’-situations. It seemingly proved the validity for all body core temperatures T<TK.The present study investigates VBT further and discovers that VBT-applicability has an upper limit in time since death. We show how to compute this upper limit explicitly in forensic casework and explain by the frequentist confidence interval probability interpretation why the former study (Potente et al., 2017 [10]) missed this upper limit.

Post-mortem chemical excitability of the iris should not be used for forensic death time diagnosis.

Post-mortem chemical excitability of the iris is one of the non-temperature-based methods in forensic diagnosis of the time since death. Although several authors reported on their findings, using different measurement methods, currently used time limits are based on a single dissertation which has recently been doubted to be applicable for forensic purpose. We investigated changes in pupil-iris ratio after application of acetylcholine (n = 79) or tropicamide (n = 58) and in controls at upper and lower time limits that are suggested in the current literature, using a digital photography-based measurement method with excellent reliability. We observed "positive," "negative," and "paradox" reactions in both intervention and control conditions at all investigated post-mortem time points, suggesting spontaneous changes in pupil size to be causative for the finding. According to our observations, post-mortem chemical excitability of the iris should not be used in forensic death time estimation, as results may cause false conclusions regarding the correct time point of death and might therefore be strongly misleading.

Uncertainty in temperature-based determination of time of death

Temperature-based estimation of time of death (ToD) can be performed either with the help of simple phenomenological models of corpse cooling or with detailed mechanistic (thermodynamic) heat transfer models. The latter are much more complex, but allow a higher accuracy of ToD estimation as in principle all relevant cooling mechanisms can be taken into account. The potentially higher accuracy depends on the accuracy of tissue and environmental parameters as well as on the geometric resolution. We investigate the impact of parameter variations and geometry representation on the estimated ToD. For this, numerical simulation of analytic heat transport models is performed on a highly detailed 3D corpse model, that has been segmented and geometrically reconstructed from a computed tomography (CT) data set, differentiating various organs and tissue types. From that and prior information available on thermal parameters and their variability, we identify the most crucial parameters to measure or estimate, and obtain an a priori uncertainty quantification for the ToD.

Improving stomach content based death time determination by maximum probability estimation

Stomach content based death time estimation (SCE), is a well-known technique in forensic sciences. Among more qualitatively oriented approaches the content percentage based method SCE by Tröger, Baur and Spann yields quantitative results and gives stochastic error measures for its outputs. This is possible since the methods estimator, which we call transformed expectation estimator (TEE) as well as the probability distribution of the time between last meal and death are determined numerically, though in SCE the estimator and confidence intervals are presented graphically only.Our articles outcomes are:-Explicit formulae of the TE estimator for SCE and of its probability distribution-Introduction of the maximum probability estimation (MPE) concept as well as of a MP estimator formula for SCE-Evidence that TEE>MPE, that the difference is more than ca.15% of the TEE and the difference can rise up to ca. 1h-Evidence that MPE is more relevant in forensic contexts than TEE

Minimum time since death when the body has either reached or closely approximated equilibrium with ambient temperature

In temperature based death time estimation the construction of a death time interval using the conventional Nomogram method (NM) is not permissible for bodies in which rectal temperature (Tr) has reached or closely approximated equilibrium with ambient temperature (Ta). We provide a logic approach to compute a minimum time since death with high probability. We also provide a simple graphical solution to be used at the crime scene for preliminary estimation. Special attention is advised in regards to cases with Ta>23°C as well as borderline cases. Proof by induction, application to test cases and one example of use are presented.

Influence of hypo- and hyperthermia on death time estimation - A simulation study.

Numerous physiological and pathological mechanisms can cause elevated or lowered body core temperatures. Deviations from the physiological level of about 37°C can influence temperature based death time estimations. However, it has not been investigated by means of thermodynamics, to which extent hypo- and hyperthermia bias death time estimates. Using numerical simulation, the present study investigates the errors inherent in temperature based death time estimation in case of elevated or lowered body core temperatures before death. The most considerable errors with regard to the normothermic model occur in the first few hours post-mortem. With decreasing body core temperature and increasing post-mortem time the error diminishes and stagnates at a nearly constant level.

Automatic CT-based finite element model generation for temperature-based death time estimation: feasibility study and sensitivity analysis.

Temperature-based death time estimation is based either on simple phenomenological models of corpse cooling or on detailed physical heat transfer models. The latter are much more complex but allow a higher accuracy of death time estimation, as in principle, all relevant cooling mechanisms can be taken into account.Here, a complete workflow for finite element-based cooling simulation is presented. The following steps are demonstrated on a CT phantom: Computer tomography (CT) scan Segmentation of the CT images for thermodynamically relevant features of individual geometries and compilation in a geometric computer-aided design (CAD) model Conversion of the segmentation result into a finite element (FE) simulation model Computation of the model cooling curve(MOD) Calculation of the cooling time(CTE) For the first time in FE-based cooling time estimation, the steps from the CT image over segmentation to FE model generation are performed semi-automatically. The cooling time calculation results are compared to cooling measurements performed on the phantoms under controlled conditions. In this context, the method is validated using a CT phantom. Some of the phantoms' thermodynamic material parameters had to be determined via independent experiments.Moreover, the impact of geometry and material parameter uncertainties on the estimated cooling time is investigated by a sensitivity analysis.