Metrological framework for selecting morphological characters to identify species and estimate developmental maturity of forensically significant insect specimens

Accurate age estimates of immature necrophagous insects associated with a human or animal body can provide evidence of how long the body has been dead. These estimates are based on species-specific details of the insects’ aging processes, and therefore require accurate species identification and developmental stage estimation. Many professionals who produce or use identified organisms as forensic evidence have little training in taxonomy or metrology, and appreciate the availability of formalized principles and standards for biological identification. Taxonomic identifications are usually most readily and economically made using categorical and qualitative morphological characters, but it may be necessary to use less convenient and potentially more ambiguous characters that are continuous and quantitative if two candidate species are closely related, or if identifying developmental stages within a species. Characters should be selected by criteria such as taxonomic specificity and metrological repeatability and relative error. We propose such a hierarchical framework, critique various measurements of immature insects, and suggest some standard approaches to determine the reliability of organismal identifications and measurements in estimating postmortem intervals. Relevant criteria for good characters include high repeatability (including low scope for ambiguity or parallax effects), pronounced discreteness, and small relative error in measurements. These same principles apply to individuation of unique objects in general.

Key points

• Metrological rigour can increase in forensic entomology by selecting measurements based on their metrological qualities.
• Selection of high-quality features for morphological identification of organisms should consider these criteria: (1) pronounced discreteness of features (minimising group overlap or maximizing interval); (2) high repeatability of assessment (such as symmetrical width rather than asymmetrical length); (3) small relative error in measurement (selecting the physically largest continuous rigid feature for measurement).
• These metrological principles also apply to individuation of unique objects in general.

     

脑震荡后综合征伤残评定研究进展

由于症状表现的主观性以及当前客观检查方法所能提供证据的匮乏,加之赔偿伴生的症状伪装和夸大等问题,脑震荡后综合征患者的伤残评定鉴定意见一致性不高.在人体损伤赔偿纠纷中,脑震荡后综合征患者的伤残评定成为法医精神病鉴定的争议点和难题.通过对脑震荡及相关术语变化、脑震荡后综合征的发生率、症状表现及诊断标准、脑震荡后综合征客观评...     

Cloud point extraction coupled with back extraction: a green methodology in analytical chemistry

Recently, cloud point extraction (CPE) coupled with back extraction (BE) has been suggested as a promising alternative to liquid-liquid extraction. In CPE, non-ionic surfactants in aqueous solutions form micelles and the solution becomes turbid when heated to the cloud point temperature. Microwave- or ultrasonic-assisted BE can be performed after CPE and before injection of the sample for instrumental analysis by ultraviolet-visible spectroscopy, high-performance liquid chromatography, gas chromatography, gas chromatography-mass spectrometry, or liquid chromatography-mass spectrometry. This article reviews selected published scientific research on the application of CPE-BE to the determination of alkaloids, drugs and organophosphorus compounds from several complex matrices. This method could be scaled-up for use in forensic science.     

Virtual anthropology: a preliminary test of macroscopic observation versus 3D surface scans and computed tomography (CT) scans

Virtual anthropology (VA) is based on applying anthropological methods currently used to analyse bones to 3D models of human remains. While great advances have been made in this endeavour in the past decade, several interrogations concerning how reliable these models are and what their proper use should be remain unanswered. In this research, a fundamental assumption of VA has been investigated: if the way we perceive and apply an anthropological method is truly similar when looking at bones macroscopically and through various 3D media. In order to answer, 10 skulls of known age and sex were scanned using a computed tomography (CT) scanner and a 3D surface scanner. Two observers separately applied a defined staging method to eight suture sites on these skulls, first looking at the bone macroscopically, then at the 3D surface scan, and finally on the CT scan. Two rounds of observation were carried out by each observer. Intra- and inter-observer error were evaluated, and two sample t-tests used to evaluate if the different types of medium used yielded significantly different observations. The results show a high degree of inter-observer error, and that data obtained from 3D surface scans differ from macroscopic observation (confidence level 95%, P ≤ 0.05). CT scans, in these settings, yielded results comparable to those obtained through macroscopic observations. These results offer many possibilities for future research, including indications on the kind of anthropological methods and anatomical landmarks that might be reliably transferable to the virtual environment. All current methods used in traditional anthropology should be tested, and if they prove unreliable, new techniques to analyse bones from virtual models should be developed.

Key points

• Large discrepancies between observation on dry bones and computer-generated 3D models (surface scans or CT scans) could lead to the re-evaluation of the suitability of traditional anthropological methods for application on 3D models.
• This preliminary study evaluates whether macroscopic, 3D surface scans, and CT scans viewings generate different observations.
• The results indicate that the data are not always coherent across all three media of observation.
• Explanations include the aspect given to the bone by the 3D software, differences between handling bones in real life versus on a computer, and level of expertise of the observers.

     

薄层螺旋CT扫描在肋骨骨折法医学鉴定中的应用分析

目的 明确薄层螺旋CT扫描及其图像后处理功能对肋骨骨折的诊断价值.方法 取2018年在本鉴定所进行肋骨骨折摄片复查的被鉴定人为研究对象,年龄为41～80岁,共计125例,所有对象均在本鉴定所进行薄层螺旋CT扫描,根据现场CT影像学检查进行图像后处理并作出诊断,采用卡方检验对相关数据进行分析.结果 本所复查的案例中,64...     

Postmortem chest computed tomography for the diagnosis of drowning:a feasibility study

It may be difficult to distinguish the cause of death in drowning cases without specific findings. The aim of this study was to explore the forensic value of thoracic postmortem computed tomography (PMCT) using routine images and three-dimensional (3D) image reconstructions. The imaging data of PMCT examinations of six drowning cadavers, aged 21–54 years, were analyzed. Twelve victims of sudden death from coronary artery disease (CAD) were chosen as a control group. After 3D bilateral lung images were reconstructed using image processing software, an interactive medical image control system was used to measure and analyze parameters including lung volume, lung volume ratio, mean CT value of the whole lung, and lung CT value distribution curves. Lung volume and lung volume ratio were used to assess the shape changes of the lung. Lung CT value distribution curves showed the corresponding number of pixels of the different CT values in the lung image. Lung volume was not significantly larger in drowning cases (mean 2 958 cm³) than in controls (mean 2 342 cm³). Lung volume ratio values in the drowning group (mean 0.3156) were greater than those in the control group (mean 0.2763); (P = 0.02). There was no significant difference between the drowning and control group in the mean CT value of the whole lung. There were differences between lung CT value distribution curves in drowning victims and controls, with drowning victims showing a single peak and CAD cases showing a bimodal distribution. Thoracic PMCT is helpful for the forensic medical diagnosis of drowning. Lung volume ratio and lung CT value distribution are potential indicators to distinguish between drowning and CAD.     

Forensic toxicological study on adipocere formation in submerged cadavers of female albino rats intoxicated with cadmium

There is a dearth of information on the mutual interaction between metal intoxication and adipocere formation. Herein, 40 adult female albino rats were distributed into two equal groups, one used as control while the other orally administered single dose of cadmium chloride (CdCl₂) 225 mg/kg·bw (LD_min). Control group was killed by cervical dislocation. Half of dead rats of both groups were subjected for determination of iodine value and estimation of cadmium (Cd) residues while the other half of both groups were submerged in opened glass container previously filled with 4 L dechlorinated tap water kept in closed room with an open air access (one cadaver/container). Gross morphological changes of submerged cadavers were recorded weekly along the experiment. At the end of the experiment, after 3 months, samples were collected again for iodine value determination and estimation of Cd residues. The obtained results revealed the depressant effect of Cd toxicity on development of adipocere. Cd residues were found in different tissues of cadavers at time of death with the highest amount in the intestines followed by the liver and kidneys, then lungs, adipose tissue, muscles, and finally the bones. After 3 months of water submersion, tissues exhibited significant decrease in the amount of Cd residues but to a limit that was still detected. This study concluded the possibility of detection of Cd residues even after adipocere formation. Additionally, it shed light on the possibility of the interference of environmental pollution with the natural rate of decomposition especially adipocere formation.     

多层螺旋CT检查在尸体颈椎损伤中的应用

对需要在尸体检验时进行颈椎多层螺旋CT(MSCT)检查的情形进行讨论,研究利用MSCT对疑有颈椎损伤的尸体进行颈椎检查的方法,并对一例疑似颈椎损伤尸体的颈椎提取后进行MSCT检查。发现对疑似有颈椎骨折尸体提取颈椎进行MSCT检查,可以快速精确地显示颈椎的细微骨折及骨折的空间分布,从而推断致伤方式。解决了传统尸检中费时费力,容易漏诊和误诊的问题。     

Significant Differences in PostMortem Heart Weight Before and After Dissection Using the Short-Axis Dissecting Method

Correctly assessing heart weight can be critical at postmortem examination. The current international guidelines advocate using the short-axis method in dissecting the heart and the heart weighed when the blood is emptied. However, it did not specify at what point the heart should be weighed or how the blood should be emptied. This study compared heart weights at three different time points during the heart examination (immediately after dissecting out of the pericardial sac with blood still in chambers, blood washed/removed from heart chambers without the heart opened, and the heart completely opened, blood emptied, and pad dried). This was to illustrate the variation in measurement and potential errors when the heart is weighed at different time of dissection. The results show that there were statistical and clinical significant differences between the heart weights at each weighing points. We recommend the heart to be completely dissected with any blood and residual washing/rinsing water emptied before being weighed. Although performed in this study, the effect of pad drying the heart on heart weight was not explored and was a limitation in this study.     

Postmortem Computed Tomography in Firearm Homicides: A Retrospective Case Series,

Postmortem computed tomography (PMCT) is integrated into the evaluation of decedents in several American medical examiner offices and medicolegal death investigative centers in many other countries. We retrospectively investigated the value of PMCT in a series of firearm homicide cases from a statewide centralized medical examiner’s office that occurred during 2016. Autopsies were performed or supervised by board-certified forensic pathologists who reviewed the PMCT scans prior to autopsy. PMCT scans were re-evaluated by a forensic radiologist blinded to the autopsy findings and scored by body region (head–neck, thoracoabdominal, and extremities). Injury discrepancies were scored using a modified Goldman classification and analyzed with McNemar’s test. We included 60 males and 20 females (median age 31 years, range 3–73). Based on PMCT, 56 (79.1%) cases had injuries relevant to the cause of death in a single body region (24 head–neck region, 32 thoracoabdominal region). Out of these 56 cases, 9 had a missed major diagnosis by PMCT outside that region, including 6 extremity injuries visible during standard external examination. Yet all had evident lethal firearm injury. We showed that PMCT identifies major firearm injuries in homicide victims and excludes injuries related to the cause of death in other regions when a single body region is injured. Although PMCT has a known limited sensitivity for soft tissue and vascular pathology, it can be combined with external examination to potentially reduce or focus dissections in some of these cases depending on the circumstances and medicolegal needs.