Forensic Entomology

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Journal of Forensic Medicine 2021, 37 (3): 293-294. DOI: 10.12116/j.issn.1004-5619.2021.410301

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Progress and Application of Entomological Evidence in Forensic Science

REN Li-pin, SHANG Yan-jie, GUO Ya-dong

Journal of Forensic Medicine 2021, 37 (3): 295-304. DOI: 10.12116/j.issn.1004-5619.2020.401001

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Entomological evidence provides entry points and clues for cases detection, in terms of estimation of the postmortem interval （PMI）, and place and cause of death. In recent years, the feasibility of entomological evidence in practice has been proved by theories and cases. It especially plays an important role in the investigation of cases with unnatural death, no monitoring, and highly corrupt cadaver. However, there are still some key issues to be further studied and standardized before the application of entomological evidence to forensic practice, to improve the effect of entomological evidence in forensic investigation and trial. This paper retrospectively reviews key studies of the application of entomological evidence in forensic science, mainly including discussion of forensic entomology inspection standard, identification studies of sarcosaprophagous insect species, collection of sarcosaprophagous insect growth and succession data under different environments and forensic entomotoxicology. With the rapid development of information technology and biotechnology, applying artificial intelligence and whole genome sequencing technology in forensic entomology has become a new research direction, which can improve the application value and range of entomological evidence in forensic science.

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Research Progress on Species Identification of Sarcosaprophagous Flies

RAN Yuan, ZHANG Xiao-yuan, LÜ Zhou

Journal of Forensic Medicine 2021, 37 (3): 305-317. DOI: 10.12116/j.issn.1004-5619.2021.410208

Abstract （474）

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Estimation of postmortem interval （PMI） has always been one of the difficult problems for forensic scientists. It is especially hard to estimate the PMI of highly decomposed corpses in the wild or in secluded houses with conventional methods. Therefore, application of insect evidence at the scene is usually required for estimation. Sarcosaprophagous flies of different species have totally different developmental rates. In actual cases, direct measurement of the body length of the larvae, calculation of accumulated temperature and succession stages without species identification, or calculation based on incorrect species identification would often lead to a large deviation between the calculated results and the real PMI. This mistake would also mislead the case investigation. Therefore, accurate species identification should be implemented before any PMI estimation of decomposed corpses with forensic entomological methods. This article reviews the general and ultramicroscopic species identification and molecular biological species identification methods of different stages of sarcosaprophagous flies, in order to provide new ideas and methods for related research and practice, and provide reference for the application and promotion of forensic entomology in the front line of public security.

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Transcriptome Sequencing Analysis of Chrysomyia Megacephala Pupae in Different Growing Periods

WANG Qi-yan, ZHANG Hong-ling, REN Zheng, et al.

Journal of Forensic Medicine 2021, 37 (3): 318-324，331. DOI: 10.12116/j.issn.1004-5619.2020.401214

Abstract （285）

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Objective To study the growth regulation, environmental adaption and epigenetic regulation of Chrysomyia Megacephala pupae, in order to obtain the transcriptome data of Chrysomyia Megacephala in different growing periods, and lay the foundation for forensic application. Methods The Chrysomyia Megacephala was cultivated and after pupation, 3 pupae were collected every 24 h from pupation to emergence, and stored at -80 ℃ for later use. High-throughput sequencing was performed by Illumina Hiseq 4000 and Unigenes were obtained. The Unigenes were compared by comparison tool BLAST from NCBI in databases such as NR, STRING, SWISS-PROT （including Pfam）, GO, COG, KEGG in order to obtain the corresponding annotation information. The expression amount of Unigenes obtained by sequencing in Chrysomyia Megacephala in six different growing periods was calculated by FPKM method, and the discrepant genes were screened according to the following standards： the log2 multiple absolute value of FPKM expression amount between two different growing periods must be larger than 1 （log2|FC|>1）, and the false discovery rate must be less than 0.05. Results When the mean temperature was 25.6 ℃, Chrysomyia Megacephala emerged 6 d after they pupated. A total of 43 408 pieces of Unigenes were obtained and their mean length was 905 bp, of which 32 500, 18 720, 13 542, 9 191 and 18 720 pieces were annotated by NR, SWISS-PORT, Pfam, STRING and KEGG databases. According to the discrepant gene analysis of pupae in two different growing periods, the number of genes with variants ranged from 801 to 5 307, and the total number of discrepant genes was 45 676. Conclusion The gene expressions of the transcriptome data of Chrysomyia Megacephala pupae in different growing periods are different. The results provided a good foundation for further research on the transcriptome changes in each period of the pupae of sarcosaprophagous flies and provided the basis for exploring the genes associated with the growth of Chrysomyia Megacephala pupae.

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Species Identification of Sarcosaprophagous Flies Based on Vein Digital Image Analysis

SHANG Yan-jie, PAN Peng-liang, LI Xiang-rong, et al.

Journal of Forensic Medicine 2021, 37 (3): 325-331. DOI: 10.12116/j.issn.1004-5619.2020.400506

Abstract （292）

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Objective To identify species of common sarcosaprophagous flies based on digital image analysis of veins, in order to provide new idea for fast and accurate species identification of sarcosaprophagous flies in forensic entomology. Methods Random trapping of 226 male and female sarcosaprophagous flies that comprised of 7 common species, including Sarcophaga peregrina, Parasarcophaga ruficornis, Sarcophaga dux, Seniorwhitea reciproca, Bercaea cruentata, Aldrichina grahami, and Synthesiomysia nudiseta with carrion in the field was conducted. The 17 landmarks on the right wing of each fly were digitally processed and the images were analyzed. The effects of allometry were evaluated using a permutation test. Wing shape variations among 7 sarcosaprophagous fly species and female species was analyzed using canonical variate analysis （CVA）. Additionally, cross-validation test was used to evaluate the reliability of classification. Results Among 7 sarcosaprophagous fly species and female species, the effect of allometry had statistical significance （P<0.05）. The CVA results showed that among 7 sarcosaprophagous fly species and female species, differences in the wing shape were significant, and the first two canonical variates accounted for 82.9% and 84.1% of the total variation of vein shape. Vein digital image analysis can be used to separate the 7 common sarcosaprophagous flies, with an overall species identification accuracy of 81.2%-100.0%, and with a species identification accuracy of 75.0%-100.0% to distinguish the female flies of the 7 sarcosaprophagous flies species. Conclusion Vein digital image analysis is a relatively convenient and reliable method for identification of insect species, which can be used for species identification of common sarcosaprophagous flies.

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Application of Sarcosaprophagous Insects to Estimate the Postmortem Interval in 11 Cases

WANG Yu, LIAO Ming-qing, WANG Ying-hui, et al.

Journal of Forensic Medicine 2021, 37 (3): 332-337. DOI: 10.12116/j.issn.1004-5619.2021.410201

Abstract （545）

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Objective To test the feasibility and accuracy of with sarcosaprophagous insects postmortem interval （PMI） estimation with sarcosaprophagous insects and provide references for estimation practice. Methods Eleven cases confirmed by the detection results, with complete entomological evidence were selected. The insect species, estimation results and true results involved in the cases were statistically analyzed and compared. Results Thirteen species of insects were found at the criminal scene, including Chrysomya megacephala （Fabricius）, Chrysomya rufifacies （Macquart）, Chrysomya nigripes （Aubertin）, Lucilia sericata （Meigen）, Hydrotaea spinigera Stein, Muscina stabulans （Fallén）, Sarcophagid （species were not identified）, Megaselia scalaris （Loew）, Hermetia illucens （Linnaeus）, Saprinus splendens （Paykull）, Creophilus maxillosus （Linnaeus）, Dermestes maculatus （De Geer） and Necrobia ruficollis （Fabricius）. The PMI of all eleven cases was within the range of estimated PMI. The estimated results of 72.73% cases were on the same day of the true results. Conclusion Sarcosaprophagous insects can estimate the PMI simply and conveniently. In cases where the PMI is within the time range of one generation of flies or beetles, the estimation results are relatively accurate. However, the estimation is less accurate when the PMI is beyond the time range.

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Application of Chrysomya rufifacies （Diptera, Calliphoridae） to Postmortem Interval Estimation in Southwest China: A Case Report

LI Xue-bo, ZHAO Feng, DING Chun-li, et al.

Journal of Forensic Medicine 2021, 37 (3): 338-343. DOI: 10.12116/j.issn.1004-5619.2020.400314

Abstract （352）

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Insect samples found on human corpses can provide the information important to estimating the minimum postmortem interval （PMImin）. A female cadaver, found in a deserted factory in Chongqing of China, was confirmed as a homicide case after the forensic investigation and autopsy. Determining the time of death was difficult due to the inconsistent degree of decomposition in different parts of the decedent. The insect specimens found on the cadaver were identified to be Chrysomya rufifacies （C. rufifacies, Macquart） by morphology and mitochondrial DNA sequence analysis. The PMImin was estimated to be 452 h, based on the developmental rate of C. rufifacies. The PMImin was estimated successfully to be almost precise, which provided an important entomological evidence for case investigation and suspect prosecution. In so doing, this highlights the usefulness of entomological evidence of specific species in the geographic area for PMI accurate estimation, especially in the case of advanced decomposed corpses.

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