Experimental and casework validation of ambient temperature corrections in forensic entomology

This paper expands on Archer (J Forensic Sci 49, 2004, 553), examining additional factors affecting ambient temperature correction of weather station data in forensic entomology. Sixteen hypothetical body discovery sites (BDSs) in Victoria and New South Wales (Australia), both in autumn and in summer, were compared to test whether the accuracy of correlation was affected by (i) length of correlation period; (ii) distance between BDS and weather station; and (iii) periodicity of ambient temperature measurements. The accuracy of correlations in data sets from real Victorian and NSW forensic entomology cases was also examined. Correlations increased weather data accuracy in all experiments, but significant differences in accuracy were found only between periodicity treatments. We found that a >5°C difference between average values of body in situ and correlation period weather station data was predictive of correlations that decreased the accuracy of ambient temperatures estimated using correlation. Practitioners should inspect their weather data sets for such differences.     

Stay cool or get hot? An applied primer for using temperature in forensic entomological case work

The reliable reconstruction of the temperature conditions at a crime scene is still a great challenge in forensic-entomological case work. Despite many published standards and guidelines for reconstructing temperature, and studies analysing the influence of various factors on the accuracy on such reconstructions, there are astonishingly many cases in the literature in which the temperature at the place of discovery is not reconstructed at all, i.e. the most common method is using the data of the nearest meteorological weather station without any correlation with on-site data. This study summarizes the state of the art in temperature reconstruction from an entomological point of view and compares the application of generalized additive models (GAMs) and linear regression on the basis of hypothetical death scenarios with various post mortem intervals (PMI) and measurement periods for the correlation between crime scene and weather station. We show that GAMs i.e. analysing the potential delay effect of temperature within a day, are the tools of choice because they give better, i.e. more accurate estimations than linear regression in 95,6% of all analysed cases regardless of the PMI, body discovery site and correlation period. Nevertheless, each case and crime scene is unique and therefore each entomological expertise should discuss the possible strengths and weaknesses of its temperature reconstruction. Even if temperature is not or cannot be reconstructed for various reasons, a comparison of on-site data with those of a meteorological weather station is the minimum forensic experts should do.     

How Should Forensic Anthropologists Correct National Weather Service Temperature Data for Use in Estimating the Postmortem Interval?

This study examines the correlation between site‐specific and retrospectively collected temperature data from the National Weather Service (NWS) over an extended time period. Using iButtonLink thermochrons (model DS1921G), hourly temperature readings were collected at 15 sites (1 validation; 14 experimental) from December 2010 to January 2012. Comparison between the site‐specific temperature data and data retrieved from an official reporter of NWS temperature data shows statistically significant differences between the two in 71.4% (10/14) of cases. The difference ranged between 0.04 and 2.81°C. Examination of both regression and simple adjustment of the mean difference over extended periods (1, 2, 3, 4, 5, 6, & 9 months) suggests that on the timescale typical in forensic anthropology cases neither method of correction is consistent or reliable and that forensic anthropologists would be better suited using uncorrected NWS temperature data when the postmortem interval is extended.     

Time of death of victims found in cold water environment

Limited data is available on the application of post-mortem temperature methods to non-standard conditions, especially in problematic real life cases in which the body of the victim is found in cold water environment. Here we present our experience on two cases with known post-mortem times. A 14-year-old girl (rectal temperature 15.5 degrees C) was found assaulted and drowned after a rainy cold night (+5 degrees C) in wet clothing (four layers) at the bottom of a shallow ditch, lying in non-flowing water. The post-mortem time turned out to be 15-16 h. Four days later, at the same time in the morning, after a cold (+/- 0 degrees C) night, a young man (rectal temperature 10.8 degrees C) was found drowned in a shallow cold drain (+4 degrees C) wearing similar clothing (four layers) and being exposed to almost similar environmental and weather conditions, except of flow (7.7 l/s or 0.3 m/s) in the drain. The post-mortem time was deduced to be 10-12 h. We tested the applicability of five practical methods to estimate time of death. Henssge's temperature-time of death nomogram method with correction factors was the most versatile and gave also most accurate results, although there is limited data on choosing of correction factors. In the first case, the right correction factor was close to 1.0 (recommended 1.1-1.2), suggesting that wet clothing acted like dry clothing in slowing down body cooling. In the second case, the right correction factor was between 0.3 and 0.5, similar to the recommended 0.35 for naked bodies in flowing water.     

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

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

Factors influencing the precision of estimating the postmortem interval using the triple-exponential formulae (TEF). Part I. A study of the effect of body variables and covering of the torso on the postmortem brain, liver and rectal cooling rates in 117 forensic cases

Brain, liver, rectal and environmental temperatures were continuously monitored under controlled conditions, in 117 forensic fatalities, for up to 60 h after death. Cases were studied either naked (63%) or covered with two blankets (37%). Bodies were classified into fat and thin groups. Statistical analysis and curve-fitting of the data yielded the average triple-exponential formulae for each body site and each body group. The effects of covering of the torso and body parameters such as weight, height, surface area and 'cooling size factor' (Z) on postmortem cooling are assessed and discussed. Results show that covering of the torso has a significant influence on the rate of postmortem cooling, however, there is no good correlation between the body variables and the cooling rate.     

Post-mortem interval estimation based on insect evidence in a quasi-indoor habitat

Insects collected on indoor cadavers are frequently used for post-mortem interval (PMI) estimation. Buildings encountered during crime investigations vary according to temperatures inside, the extent of insect access restriction or sanitary conditions. This article reports the PMI oriented analyses of insect evidence sampled from the human cadaver in the atypical indoor habitat. The body was found in the uninhabited house, on the floor covered with rubbish, in the room with no doors and windows. Thermal conditions in the room were less variable than in the local weather station, however still much more variable compared to the typical indoor habitat, indicating the need for retrospective correction of temperature records from the station. Cadaver entomofauna was surprisingly diverse and abundant. We recorded several taxa usually not occurring on indoor cadavers, e.g. immature stages of Necrodes littoralis (Coleoptera: Silphidae) or Stearibia nigriceps (Diptera: Piophilidae). PMI was based on the age and the pre-appearance interval estimated for live puparium of S. nigriceps, giving the total interval of 37 (±7.4) days plus 4–20?days resulting from the absence of first colonizing specimens of the species. This estimate was corroborated with the age estimate for empty puparia of Sarcophaga argyrostoma (Diptera: Sarcophagidae) with traces of Nasonia sp. (Hymenoptera: Pteromalidae) eclosion. Other insects indicated shorter but consistent PMI. Difficulties and limitations of insect-based PMI estimations in unusual indoor habitats are discussed.     

石河子春季常见尸食性昆虫种类及丝光绿蝇发育观察

目的观察新疆石河子市区尸食性昆虫的种类及温度对优势种丝光绿蝇生长发育的影响。方法 2007年和2008年的4月15日至6月15日在石河子市（E44.18°、N86.00°）3个不同地点诱集尸食性昆虫,并鉴定分类。将优势种丝光绿蝇在不同温度下饲养,观察其体长、体重、羽化率、雌雄比、历期等生长发育特点。结果石河子地区春季3个不同地点共诱集到尸食性昆虫6目14科16种,其中以膜翅目、双翅目和鞘翅目为主;丝光绿蝇幼虫体长、体重随着温度升高而增长、增加,化蛹时又有所缩短、减轻;不同的温度对幼虫的羽化率和雌雄比影响不明显。结论本文所得数据可为新疆石河子地区的法医昆虫学及相关研究和实践提供一定参考。     

Reconstruction of a real car-pedestrian-accident. Part 2: Modelling and simulation

A real pedestrian-car-crash was reconstructed by use of a multi-body simulation. The main aspect was the use of an individual body surface for the human body model and the car. The simulation allowed a plausible reconstruction of the accident. A good correlation of the contact-pairs in the model and the real forensic data was achieved by variation of the hypothetical szenario.     

Site-dependent postmortem changes in blood cocaine concentrations

When a forensic toxicologist interprets postmortem blood cocaine findings he usually must make assumptions regarding perimortem drug concentrations. In-vitro studies have shown that cocaine rapidly hydrolyzes in unpreserved blood, particularly at elevated temperatures. However, other studies have demonstrated site-dependent postmortem release of some drugs from tissue stores accompanied by increases in drug concentrations in the blood. This study was undertaken to investigate whether blood cocaine concentrations change in the body during the postmortem interval and, if so, to measure the direction and magnitude of the changes. In medical examiner cases in which scene investigation suggested that the decreased was a cocaine user, blood samples were collected as soon after death as possible. At autopsy, a second set of samples was collected. Analysis of paired samples by gas chromatography/mass spectrometry (GC/MS) revealed dramatic differences in the cocaine concentration. The magnitude and direction of the change appears to be site dependent. Usually, but not invariably, cocaine concentration in subclavian vein blood decreases while that in heart, aorta, and femoral vein blood increases during the interval between death and autopsy. The findings emphasize the danger inherent in attempting to estimate the concentration of cocaine in blood at the time of death from postmortem data.     

Retrospective analysis of factors affecting rate of skeletonization within a tropical climate

Estimating the post mortem interval (PMI) in skeletonized cases is an extremely challenging exercise. Sri Lanka lacks adequate taphonomic research which is a serious limitation when assessing PMI in forensic death investigations. Methods that have been proposed to estimate PMI using the total body score (TBS) and accumulated degree days (ADD) are mainly based on data from continental and temperate climates and have shown less reliability in tropical climates. With the intention of developing a region-specific, evidence-based guide which would be applicable to tropical climates like Sri Lanka, we selected thirteen skeletonized remains with known PMIs from forensic case records and analysed their taphonomy in relation to selected weather data. We also compared the ADD values within our dataset with reference ranges calculated using published formula.All except one were found from outdoor locations. The TBS ranged from 24 to 32 and had a weak positive correlation with the PMI. The earliest appearance of skeletonization was 15 days in a body found indoors. The highest rate of skeletonization was seen in a body with a TBS of 32 and a PMI of 23 days. The average daily temperature and relative humidity were similar across all the cases however, the amount of rainfall varied. Bodies exposed to monsoon rains (n = 6) had a lower mean rate of skeletonization compared to those that were not exposed (n = 4) suggesting lower rates of decomposition during periods of heavy rainfall.No correlation was found between ADD and TBS. In 9 (69.2%) cases, the actual ADD was much lower than reference ADD ranges for TBS values, indicating poor applicability of TBS and ADD based formulae in estimating PMI within the Sri Lankan climate. Our study shows a strong need for taphonomic and entomological research in tropical climates to further explore the impact of monsoons on biotic and abiotic factors affecting skeletonization.     

Persistence of transferred fragrance on fabrics for forensic reconstruction applications

It has recently been established that volatile organic compounds (VOCs) successfully transfer between clothing even with a short contact of 10 s, highlighting the potential to use VOCs in forensic reconstruction scenarios, such as sexual assault cases. The mid and low volatility compounds transferred in greater amounts than high volatility compounds. This study presents empirical data addressing the persistence of transferred VOCs on clothing for the first time. A series of experiments were carried out to determine the persistence of VOCs on clothing for time periods of up 4 weeks, on natural and synthetic fibres, and at three different environmental temperatures. The data indicate that the highest VOC amounts are generally obtained for shorter persistence times of up to 1 d. Whilst high volatility compounds were not recovered in sufficient amounts to allow quantification, the four other transferred VOCs were successfully quantified for persistence times of up to 4 weeks. The persistence for mid-volatility compounds follows decay curve trends in line with those previously obtained for fibres, glass and pollen. When comparing the persistence of VOCs on a natural and a synthetic fibre, for a persistence time of 1 h, the transferred VOCs were retained on a natural fibre in higher amounts than on a synthetic fibre. However, for longer persistence times the concentration of VOCs was similar between the two fabrics. Lastly, lower environmental temperatures resulted in higher recoveries for most VOCs, especially for short persistence times. These findings demonstrate that optimal recovery of VOCs from clothing occurs when the fabric is kept at cooler temperatures and analysed soon after the fragrance transfer occurred, although VOC recovery was possible at higher temperatures and after longer persistence times. Given the transfer and persistence characteristics of VOCs from fragrance, there is potential for fragrance to be used as a form of trace in forensic reconstruction approaches.     

Width as an alternative measurement to length for post-mortem interval estimations using Calliphora augur (Diptera: Calliphoridae) larvae

The length of fly larvae collected from corpses is often used to help provide an entomological estimate of time since death. However, 'head-curling' by larvae can affect the accuracy of length measurements. To investigate a possible resolution to this problem, larvae of Calliphora augur were grown on sheep's liver at two constant temperatures (20 and 25 degrees C). Replicate samples were collected at set time intervals until pupation. Body length and width were measured for individual larvae and examined as predictors of age. It was found that body width, as measured at the junction of the fifth and sixth abdominal segments, is comparable with body length for age prediction of maggots of C. augur grown at these temperatures. Furthermore, conversion of width to length can be done with 95% accuracy from a simple linear model.     

大鼠脑损伤后COX-2表达变化的时间规律性研究

目的探讨大鼠脑损伤后环氧合酶2(COX-2)在神经元、神经胶质细胞中表达变化的时间规律性。方法以冲击应力σd为355.09kPa致大鼠脑损伤后,于不同时间段分别应用原位杂交、免疫组化、免疫组化双染色技术检测COX-2mRNA和蛋白的表达强度,用图像分析系统测定阳性反应物平均灰度,进行统计学处理。结果正常对照组COX-2mRNA和蛋白弱表达,伤后15min开始表达呈增强趋势,分别于伤后1,2d,表达达到峰值,平均灰度值分别为126.38±1.36、124.77±3.20,与对照组、邻近上组比较均具有显著性差异(P<0.05),于伤后3,4d,表达达到另一峰值,平均灰度值分别为127.18±1.96、120.14±3.52,并维持高水平表达分别至伤后7,15d,平均灰度值分别为110.03±2.61、111.27±2.83,与对照组比较具有显著性差异(P<0.05)。阳性细胞多为神经元。结论脑损伤后COX-2mRNA及蛋白的表达具有时间规律性,可作为法医学推断脑损伤形成时间的指标。     

Estimation of the post mortem period by multiple-site temperature measurements and the use of a new algorithm

The estimation of the post mortem period, in cases where death occurred under suspicious circumstances, is usually attempted using temperature measurements taken at a single body site. Early investigations of the validity of such an approach use the abdominal skin surface, the axilla and the rectum as measurement sites (B.H. Knight, Forensic Sci. Int., 36 (1987) 47-55). However, it has recently become more common to use the rectum alone, though the ear and the nasal passages have also been utilized. Whatever site is employed, the estimates are frequently found to be inaccurate. There are several fundamental reasons for these inaccuracies, the most prominent being the unknown variation in the ambient temperature between the time of death and the commencement of measurements, and the unknown body temperature at the time of death. This paper proposes a method of overcoming the above difficulties by taking a series of measurements concurrently at a number of body sites, a technique used by several previous workers (B.H. Knight, Forensic Sci. Int., 36 (1987) 47-55). Initial investigations have shown that an improved estimation of post mortem period is obtainable by the application of a suitable decision-making algorithm.     

Validation of a new method of providing case-specific time-of-death estimates using cadaver temperatures

The near ubiquitous presence of numerical simulation has made case-specific calculations of body temperatures following death possible so that accurate calculations of body temperatures can provide valuable information for estimating the time of death and can aid in forensic investigations. Here, a computational approach is described that has been validated against multiple, independent, and experimental investigations. The approach only requires one subjective input parameter (the heat transfer coefficient). A simple algorithm serves as a guidepost to the selection of this parameter. The algorithm incorporates clothing and the space in which the body is housed. Heat transfer coefficients that range from h = 2 W/m²/°C for bodies that are heavily clothed to h = 9 W/m²/°C for bodies that are nude (in air). The method also requires setting of ambient temperature conditions (ambient temperature)—however, that input is often available. The paucity of inputs makes this technique remarkably easy to employ. The new method is also able to calculate cadaver cooling rates for situations where the cadaver is in a timewise or spatially changing thermal environment (diurnal temperature variations, bodies partially submerged in water, changes to weather, insolation, etc.). Results from the present calculations are compared with a large body of measurements from the literature; it was found that the predictions and measurements were in excellent agreement, regardless of the ambient temperature conditions and the nature of the clothing of the body. This new calculation approach can be used with reasonable accuracy for determining cadaver cooling and time since death.     

Assessing temporal and weather influences on property crime in Beijing,China

Though the relationships between environment and crime have been studied a lot in many countries, this work is still a void in China. This work presents the study about how property crimes are influenced by the temporal and weather factors in China. With the crime data collected from police, the property crimes pattern by season of year, day of week and time of day are investigated firstly. Then the influence of the temporal variables—major holidays, school close days and weekends—and weather on the crimes are tested. The findings show that the robbery is significantly influenced by the temporal variables but has no correlations with weather, while burglary is not only affected by the temporal variables but also correlated with sun light hours.     

基于积分光密度的印文墨迹历时变化初步研究

目的 探讨利用积分光密度值判断印文形成时间的可行性,方法通过实验,利用Image-pro plus软件对不同时间段实验样本的印文积分光密度值数据进行采集、录入,并运用相关数据分析方法,对实验用三种品牌印油、印泥盖印印文的积分光密度值数据进行统计、分析.结果 发现在1～120d间数值下降速度较快,在120～380d间数值...     

Estimating the Time of Death in Domestic Canines

Abstract:  Because 36.1% of U.S. households have dogs, the time of death (TOD) of dogs at crime scenes can be useful to forensic investigators. However, there are few published studies based on postmortem changes in dogs. This study, conducted indoors in still air at approximately room temperature, monitored the postmortem reduction in rectal, liver, brain, and aural temperatures in 16 dogs for 32 h after death. Graphs of temperature reduction were prepared to estimate the TOD of dogs within the first 32 h postmortem. Sex, body mass, and hair coat density did not affect the rate of body temperature reduction, but increased body weight and volume slowed it. Rectal temperature was the most convenient, reasonable site for measuring body temperature. Vitreous humor potassium ion concentration [K⁺] was measured in both eyes at c.  1.5 and 7 h after death. Both eyes had the same [K⁺] when measured simultaneously, and [K⁺] increased after death.