Caddisflies assist with homicide case: determining a postmortem submersion interval using aquatic insects

Although few indicators of time since death for corpses found in aquatic ecosystems are comparable in precision to the insect indicators used in terrestrial cases, there are observations that can be useful in suggesting or ruling out an approximate PMSI (postmortem submersion interval). For example, the time intervals required for certain growth phases of aquatic insects, such as caddisflies, that may attach themselves to the submerged remains can be used to estimate a minimum PMSI. Approximately 8 of the 13 orders of insects containing species with aquatic or semi-aquatic stages are likely to be associated with carrion or corpses in aquatic habitats. We present a case study in which portions of a body from an adult male were discovered in a south central Michigan stream. The body was dismembered and portions were recovered from two bags floating and submerged in the stream. Insect specimens collected from mesh and plastic bags consisted of one fly larva belonging to the family Muscidae, and caddisfly larvae belonging to two families: the Limnephilidae. (case-makers) and the Hydropsychidae, (net spinners). We used unique case-building behaviors of the limnephilid caddisflies found on the remains to elucidate a PMSI range consistent with the disappearance of the victim. It is important for forensic investigators to understand that although some precision is lost in estimating a PMSI with aquatic insects, these organisms should not be ignored in gathering evidence from aquatic crime scenes, and in fact, they can provide valuable details in estimating a PMSI.     

Pig decomposition in lotic aquatic systems: the potential use of algal growth in establishing a postmortem submersion interval (PMSI)

While algal community composition has been examined as a qualitative indicator of postmortem submersion interval (PMSI), there have been no quantitative studies on using algal growth rates as PMSI estimators. The present study was undertaken to examine pig decomposition in streams and to develop a more quantitative approach to estimate a PMSI. Pigs and ceramic tiles were completely submerged and regularly sampled for periphyton growth. Five stages of decomposition were identified for the submerged pig carcasses according to physical characteristics. Algal growth rates, measured quantitatively as a function of chlorophyll-a concentration, were greater on pigs compared with tiles; however, microhabitat (pools versus riffles) did not significantly influence algal growth. Additionally, there was a strong correlation between algal growth rate and time on pigs and tile substrates. This strong correlation was observed after significant rain events. Our study documents for the first time a quantitative technique to determine the length of time a corpse has been submerged in water. We suggest that algal growth rates may be a useful quantitative indicator in criminal investigations involving corpses that are completely submerged in stream or riverine habitats.     

Marine bacterial succession as a potential indicator of postmortem submersion interval

The process of decomposition of bodies in the marine environment is poorly understood and almost nothing is currently known about the microorganisms involved. This study aimed to investigate the microbes involved in decomposition in the sea and to evaluate the potential use of marine bacterial succession for postmortem submersion interval (PMSI) estimation, for which there is currently no reliable method. Partial pig remains were completely submerged during autumn and winter and were regularly sampled to document marine bacterial colonisation and the changes in community composition over time. Five stages of decomposition were recognised, some of which exhibited characters specific for partial carrion. Marine bacteria rapidly colonised the submerged remains in a successional manner. Seasonal differences were observed for the rate of decomposition and also for several groups of colonising bacteria. Marine bacteria specific for particular PMSIs were identified. This study provides an insight into the involvement of saprophytic marine bacteria in the decomposition of mammalian remains in the sea and is the first to explore the use of marine bacterial colonisation and succession as a novel tool for PMSI estimation. We propose that with further study, marine bacterial succession will prove useful for determination of the length of time a body may have been immersed in a marine environment.     

Survival of submerged blowfly species and their parasitoids: implications for postmortem submersion interval

Pupal survival of three blowfly species, Chrysomya albiceps, Chrysomya megacephala, and Chrysomya putoria (Diptera: Calliphoridae) and the parasitoid species Nasonia vitripennis (Hymenoptera: Pteromalidae) was studied after the pupae were experimentally submerged in water. Non-parasitized pupae at different developmental stages, 0, 24, 48, and 72 h, and parasitized pupae after 3, 8, 10, and 12 days of development were submerged for 6, 24, 48, or 72 h. Control groups for each pupal developmental stage (parasitized or not), which were not submerged, were also observed in order to compare the adult emergence rates. The survival of white pupae (0 h/age) decreased with time of submergence for all three blowfly species, showing the lowest rates compared with other experimental pupa groups. For the three blowfly species, non-parasitized pupae at 24 and 48 h of age showed survival rates above 60%. However, for pupae at 72 h of age, the survival rates decreased with increased underwater time, with less than 30% survival after 72 h in C. putoria and C. albiceps. The survival of parasitoids inside blowfly pupae that were submerged during their larval stage (3 days/age) decreased with the increase of submergence time. After the parasitoids reached the pre-pupal life stage, the survival was higher for all underwater periods. These observations can be useful in investigations of the decomposition of partially submerged bodies, or in cases of pupae found adhering to decaying flesh, hair, or clothes of corpses that were submerged after the larvae had developed and pupated.     

Comparison of chemical methods for determining postmortem interval

Accurate determination of postmortem interval (PMI) is a problem for the forensic thanatologist, especially in unwitnessed deaths. A number of objective chemical methods for determining PMI have been developed, the most widely used being accumulation of potassium in the vitreous humor. The authors previously have reported a chemical method for determining PMI from the predictable accumulation or clearance of the dopaminergic metabolite 3-methoxytyramine (3-MT) in the putamen of the brain. They have extended their previous study to compare directly the accuracy of determining PMI from the level of 3-MT in putamen with the level of potassium in vitreous humor. The data indicate that 3-MT is at least as accurate as, if not more accurate than, potassium accumulation in vitreous humor, although 3-MT levels can be affected by the cause of death and drugs present at the time of death. Nevertheless, determination of both the 3-MT and potassium levels can afford the most accurate method of determining PMI; preliminary nomograms for determining PMI from both variables are presented.     

Morphine extraction in necrophagous insects remains for determining ante-mortem opiate intoxication.

To study the potential use of insects remains as toxicological indicators, we measured morphine in desiccated entomological materials using a radioimmunoassay method (Coat-A-Count Serum Morphine, Dade Behring, France) following enzymatic hydrolysis.First, enzymatic cuticle extraction of morphine (pronase digestion preceded by a 2h incubation with a dithiothreitol solution) was performed on various substrates (Calliphoridae puparial cases and desiccated adults, and desiccated pupae of Dermestidae) which were then tested to identify possible interferences with the radioimmunoassay procedure.This same procedure was performed on puparial cases and desiccated adults of Lucilia sericata (Diptera, Calliphoridae) previously reared on minced meat containing various morphine concentrations. Morphine was detected only in cuticle powder from insects reared on meats containing 100 and 1000mg/kg. Higher concentrations were measured in puparial cases. Rearings on psoas from eight heroin overdose victims confirmed previous experimental results.Remains of necrophagous insects, particularly puparial cases, are often preserved for a long time, and consequently can serve as late alternative specimens for toxicological analysis when suitable tissues are not available.     

The potential to determine a postmortem submersion interval based on algal/diatom diversity on decomposing mammalian carcasses in brackish ponds in Delaware

Recently botanical evidence has been studied to determine if it is useful in forensic investigations. This study was performed to examine stillborn piglet decomposition in a brackish water environment and to semi-quantitatively document stages of decomposition, degree day accumulation per stage as well as the algal/diatom diversity useful in determining a postmortem submersion interval (PMSI). Piglets and ceramic tiles were submerged in brackish ponds and sampled on a regular basis to document algal diversity and succession between substrates and stages of decomposition. Significantly greater weight was lost from piglet carcasses during the early floating and advanced floating decay stages. Seasonal effects were observed in degree-day accumulations. Diatom diversity was significantly greater on piglet carcasses compared to tile substrates. Algal diversity decreased over time on the piglet carcasses as well as the stage of decomposition. A significant relationship and strong correlation between algal diversity found on the piglet substrate with time was observed. Our results indicate that more research is needed to examine the potential to use diatoms in not only determining manner of death but also the duration of time (PMSI) a victim may have been immersed in an aquatic environment.     

Decomposition chemistry of human remains: a new methodology for determining the postmortem interval

This study was conducted to characterize the chemistry associated with the decomposition of human remains with the objective of identifying time-dependent biomarkers of decomposition. The purpose of this work was to develop an accurate and precise method for measuring the postmortem interval (PMI) of human remains. Eighteen subjects were placed within a decay research facility throughout a four-year time period and allowed to decompose naturally. Field autopsies were performed and tissue samples were regularly collected until the tissues decomposed to the point where they were no longer recognizable (encompassing a cumulative degree hour (CDH) range of approximately 1000 (approximately 3 weeks)). Analysis of the biomarkers (amino acids, neurotransmitters, and decompositional by-products) in various organs (liver, kidney, heart, brain, muscle) revealed distinct patterns useful for determining the PMI when based on CDHs. Proper use of the methods described herein allow for PMIs so accurate that the estimate is limited by the ability to obtain correct temperature data at a crime scene rather than sample variability.     

图像分析技术测定DNA含量变化推断死亡时间的研究及应用前景

图像分析技术是20世纪50年代发展起来的一门技术,它通过对图像信息的收集、处理、计算、分析而得出图像各部分的数量变化,在生物医学领域已经成为一种常规的定量技术。本文对图像分析技术测定DNA含量的原理、死后细胞核DNA降解的规律及图像分析技术定量DNA推断死亡时间的应用前景进行了综述。     

大鼠脑、骨髓细胞核DNA降解推断死后间隔时间的研究

目的检测大鼠死后不同温度下脑、骨髓细胞核DNA降解规律，寻找推断早期死亡间隔时间（PMI）的新参数。方法10℃和20℃下，大鼠死后0～40h内，每隔4h取材脑组织和骨髓，单细胞凝胶电泳（SCGE）检测DNA降解程度，线性回归分析比较彗星参数HeadDNA％、尾长（TL）、Olive尾矩（TM）与PMI的关系。结果大鼠死后早期脑细胞、骨髓细胞核Head DNA％随着PMI逐渐下降的程度不同，20℃脑细胞核Head DNA％降解速率较快。与骨髓细胞相比，脑细胞核Head DNA％与PMI线性关系较好。与TL、TM相比，Head DNA％与PMI的线性关系较好。结论脑组织是利用SCGE检测DNA降解推断PMI的合适检材。Head DNA％较TL、TM推断PMI的价值更高。     

Use of combined frequencies for RFLP and PCR based loci in determining match probability

Statistical analysis was performed on a subset of the Pennsylvania State Police Caucasian, African American and Hispanic database for the purpose of determining Hardy-Weinberg equilibrium and associations across the RFLP loci D1S7, D2S44, D4S139, D5S110, D10S28 and D17S79 and the PCR-based loci HLA-DQA1, LDLR, GYPA, HBGG, D7S8 and Gc. Overall, the statistical results are consistent with a population in equilibrium both within and between loci. The assumption for independence is valid.     

Succession pattern of carrion-feeding insects in Paramo, Colombia

The minimum postmortem interval can be estimated based on knowledge of the pattern of insect succession on a corpse. To use this approach requires that we take into account the rates of insect development associated with particular climatological conditions of the region. This study is the first to look at insect succession on decomposing carcasses in the high altitude plains (Paramo) in Colombia, at 3035 m above sea level. Five stages of decomposition were designated with indicator species identified for each stage: Callíphora nigribasis at the fresh stage; Compsomyiops verena at the bloated stage; Compsomyiops boliviana during active decay; Stearibia nigriceps and Hydrotaea sp. during advanced decay and Leptocera sp. for dry remains. A succession table is presented for carrion-associated species of the region, which can be used for estimating time since death in similar areas. Compsomyiops boliviana is reported for the first time in Colombia.     

mtDNA多态性在嗜尸性昆虫种类鉴定中的应用

嗜尸性昆虫的种类鉴定是利用昆虫学知识进行法医学研究的重要步骤之一.近年来研究表明,利用分子生物学技术,特别是线粒体DNA(mitochondrial DNA,mtDNA)序列分析技术对嗜尸性昆虫进行种类鉴别,能够得到较好的效果.本文对嗜尸性昆虫mtDNA的分子生物学特性、结构以及嗜尸性昆虫种类鉴定中常用的mtDNA序列...     

尸源性昆虫的法医学研究进展

尸源性昆虫学是应用昆虫学知识解决有关法律问题的法医学分支学科,对死亡时间的推断。特别是腐败尸体的死后间隔时间的推断等方面具有无可比拟的优越性。本文根据国内外近期法医昆虫学方面的研究进展,阐述了尸源性昆虫的研究历史、种类和侵蚀过程,并总结了尸源性昆虫形态学及分子生物学的种属鉴定方法。及近几年来在推断死亡时间方面的具体应用。就尸源性昆虫在法医学领域内的应用及进展进行综述。     

Method of determining methemoglobin in cadaver blood

Poisoning with methemoglobin toxins are not rare in forensic medical practice, but there is still no reliable method for measuring methemoglobin in cadaveric biological fluids and tissues. The author investigated factors affecting evaluation of natural amounts of methemoglobin in the blood, compared several methods for methemoglobin measurements, and developed qualitative characteristics indicating the presence of methemoglobin in cadaveric blood. A rational method for measuring methemoglobin in the blood, blood clots, and tissues is offered for forensic chemical and biochemical evaluations.     

石家庄地区夏秋季常见嗜尸性昆虫群落演替规律

目的研究石家庄地区常见嗜尸性昆虫种类及其群落演替。方法观察法研究2007—2009年夏秋季放置在同一地点的9只家兔尸体上常见嗜尸性昆虫的种群演替。结果该地区家兔尸体上出现常见双翅目3科4属9种,主要有蝇科的家蝇、厩腐蝇、开普黑蝇、厚环黑蝇;丽蝇科的丝光绿蝇、大头金蝇,麻蝇科的棕尾别麻蝇、肥须亚麻蝇、黑尾黑麻蝇。鞘翅目5科11种,主要有埋葬甲科的大黑葬甲、Silpha carinata（Herbst）、大负葬甲、Ptomascopus morio（Kraatz）、双色葬甲;蜣螂科的金龟子;步甲科的毛婪步甲和蠋步甲;拟步甲科的细土潜;隐翅甲科的大黑隐翅虫、小隐翅虫。膜翅目2科2种,蚁科的路舍蚁;胡蜂科的墨胸胡蜂。结论该地区嗜尸性蝇类群落演替明显,嗜尸性昆虫有地域特征。研究结果可作为石家庄地区对尸体进行死亡时间推断的依据。     

DNA定量技术在死亡时间推断中的研究进展

死亡时间推断是法医病理学研究的热点及难点之一.随着分子生物学技术的发展,DNA的定量已广泛应用于死亡时间推断的研究.本文主要对机体死后不同组织和器官中DNA含量随时间的降解情况,以及单细胞凝胶电泳、Feulgen染色图像分析技术、流式细胞仪等近年来新的DNA定量技术应用于死亡时间推断研究中的进展进行了综述.     

Accuracy in determining long-range firing position of gunman

Treating the example of a 9 mm Parabellum bullet, the paper deals with the problem of shot distance determination at long ranges. It discusses the effects of inaccurately known angles of incidence as well as of weather and ammunition data and shows that the results of computations can only indicate a certain limited area as the possible position of the shooter.