In the late Qing Dynasty,the traditional coroner system faced many problems such as technical limitation,diplomatic pressure and lack of available qualified personnel.Driven by advocates such as Xu Shichang and other ministers,the Legal Ministry approved the establishment of inspection and learning institutes in various province.The Beijing Forensic Medicine School,located in Beijing,was prepared by the General Prosecutor's Office and subjected to approval by the Legal Ministry,which was a special case among many inspection and learning institutes at that time.The curriculum for students of the Beijing Forensic Medicine School was notably broad.Beyong studying the traditional Washing Away of Wrongs(Xiyuan Lu)they also acquired knowledge and skills in,forensic medicine,criminal law and experimental subjects.

Objective This study analyzed the chemical structures of two unknown substances in e-liquid using methods such as nuclear magnetic resonance(NMR),infrared spectroscopy(IR),and mass spectrometry(MS).Methods After separating,purifying,and freeze-drying two suspicious substances from e-liquid,GC-MS analysis was used to obtain the mass spectrum characteristic ion fragments and fragmentation patterns of unknown compounds.The precise mass numbers were measured by high-resolution mass spectrometry,and proton numbers and their assignments,carbon types,and fluorine atom numbers and positions were obtained by combining 1HNMR,13CNMR,and 19FNMR.The functional groups were then analyzed by infrared spectroscopy.Results Through data analysis,the molecular formulas of the two suspicious substances are C13H13FN2O2 and C14H15FN2O2,respectively.Their structures were determined to be etomidate derivatives:1-(o-fluoromethylphenyl)imidazole-5-carboxylic acid methyl ester and 1-(o-fluoromethylphenyl)imidazole-5-carboxylic acid ethyl ester.Conclusion The structural data of two substances obtained in this study in terms of mass spectrometry,nuclear magnetic resonance,and infrared spectroscopy provide support for combating crimes involving the two substances,and provide reference for the regulation and detection of the two drugs.

Objective To evaluate the consistency of DNA coding region single nucleotide polymorphism(cSNP)genotyping at the DNA and RNA levels in common body fluid samples based on the next-generation sequencing platform.Methods After extensive literature retrieval,25 cSNP loci of 8 human tissue-specific mRNAs in peripheral blood,semen and vaginal secretion were selected.Two cSNP multiplex genotyping panels based on DNA and RNA,respectively,were developed for use on the MiSeq FGx sequencing platform.45 body fluid samples(including 14 peripheral blood samples,15 semen samples and 16 vaginal secretion samples)were sequenced and analyzed.The inconsistent typing results of DNA and RNA were rechecked by Sanger sequencing.Results The results of cSNP genotyping at the DNA and RNA levels in peripheral blood were completely consistent.Among the 15 semen samples,the genotypes of rs1995640 and rs 1995641 on the TGM4 gene were inconsistent in 3 cases.Among the 16 vaginal secretion samples,there were 2 cases,1 case and 2 case with inconsistent results of rs3869098,rs10947121 and rs12110470 in MUC22 gene,respectively.Conclusion In this study,MiSeq FGx sequencing and Sanger sequencing were used to test 25 cSNP loci with body fluid tissue specificity.The same typing results at the DNA and RNA levels were observed at 20 cSNPs.Inconsistent genotypes at the DNA and RNA levels were observed at 5 cSNPs on the TGM4 and MUC22 genes.This study provides experimental methods and data for forensic cSNP studies.

Objective To find and select stable and specific identification indexes in chest CT images,to establish mathematical models and provide a systematic and scientific identification method.Methods Medical imaging analysis and processing technology were applied to compare the image indexes such as lung apical shadow,double lung texture,trachea,sternum,thoracic morphology,liver,spleen,interlobular fissure morphology,first rib,aorta and thoracic vertebrae morphology of 600 serial chest CT scans of of the same adults at different periods and 600 scans of different adults.Consistency test(Kappa analysis)was applied to determine the consistency of different identification indexes,and to screen out the image identification indexes that were not easily affected by subjective factors and had high consistency;the cumulative exclusion probability method was applied to calculate the combined identification ability of the observation indexes,and select optimal indexes to establish the identification index system.Results Five indexes-left lung texture,right lung texture,interlobular fissure of the liver,first rib on the left side,and first rib on the right side demonstrated high consistency across age groups and minimal subjective interference.A combination of any three indexes achieved＞99.99％discrimination probability for homologous versus non-homologous sources identification.Conclusion The independent or combined use of the indexes of left lung texture,right lung texture,interlobular fissure of the liver,first rib on the left side,and first rib on the right side enables individual identification in adult chest CT under different imaging conditions.

Objective To conduct an in-depth analysis of the characteristics of skin avulsion injury in traffic accident death cases,and provide support for the inspection and identification of avulsion injury in traffic accidents.Methods Statistical analysis was performed on case data including gender,age,mode of transportation,injury location,injury mechanism in traffic accident death cases with skin avulsion injury.Results In fatal traffic accidents,the incidence of skin avulsion injury was 30.16％,the occurrence rate was higher in multiple-impact accidents compared to single-impact incidents.Skin avulsion injury were more common in pedestrian injuries,and skin avulsion injury were common due to crushing.The thigh was the most common site of skin avulsion injury.Conclusion In the examination of victims in traffic accidents,it is of great significance to discover avulsion injury and analyze their injury mechanisms for the reconstruction of traffic accident scenes.

Objective To establish a method for the simultaneous determination of 16 cephalosporin antibiotics of the fourth generation in whole blood by ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS),including representative drugs such as cefalexin,cefuroxime axetil,cefetamet pivoxil,ceftizoxime,cefodizime,cefteram pivoxil,cefpodoxime proxetil,cefditoren pivoxil,cefminox sodium,cefoperazone,cefpirome,cefoxitin,cefamandole nafate,cefquinome sulfate,cefpiramide,and ceftiofur.Methods Whole blood was pretreated with acetonitrile for protein precipitation and then determined by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry.The liquid phase used a Hypersil GOLD? C18 column(2.1 mm ×100 mm,1.9 μm).The organic phase was 0.1％formic acid methanol solution,and the aqueous phase was 0.1％formic acid aqueous solution(containing 10 mmol/mL ammonium formate)for gradient elution.Detection was performed in electrospray positive ionization mode with selected reaction monitoring(SRM).Results The 16 drugs showed good linearity within their respective concentration ranges,with R2 values all greater than 0.99.Limits of detection for cefminox sodium and cefpiramide were 50 and 20 ng/mL,respectively,and for the remaining 14 drugs were all lower than 5 ng/mL.The relative standard deviations(RSDs)of intra-day and inter-day precisions at four spiked concentrations for the 16 drugs were all no higher than 10％(n=5).Accuracy ranged within±15％for mosg drugs,except for cefamandole nafate,ceftiofur,and cefetamet pivoxil at the lower limit of quantification,which showed accuracy within±20％.Extraction recoveries exceeded 80％for all compounds.Conclusion This method has high detection sensitivity,rapid speed,and good repeatability for the simultaneously determination of 16 cephalosporin antibiotics in whole blood.

Objective To develop a gas chromatography-tandem mass spectrometry(GC-MS/MS)method for the simultaneous determination of ephedrine and pseudoephedrine in urine.Methods Urine samples containing ephedrine and pseudoephedrine components were extracted with ethyl acetate,centrifuged to collect the supernatant and evaporated to dryness under a nitrogen stream and then derivatized with heptafluorobutyric anhydride 60 μL at 70 ℃ for 30 min,and re-evaporated under nitrogen,and then solubilized with 50 μL of methanol,and then analyzed by GC-MS/MS.Results The method demonstraed excellent linearity for ephedrine(0.05～10 μg/mL,r=0.999 8)and pseudoephedrine(0.02～5 μg/mL,r=0.999 5).Extraction recoveries ranged from 89.4％～95.8％(ephedrine)and 90.3％～93.8％(pseudoephedrine).Limits of detection and quantification of ephedrine and pseudoephedrine were 0.005 μg/mL and 0.01 μg/mL,the intra-day precision and accuracy were less than 5.87％and 9.56％,respectively,and the inter-day precision and accuracy were less than 7.54％and 9.27％,respectively.The stability of ephedrine and pseudoephedrine in urine in 15 d was good under the conditions of room temperature and-20 ℃.Conclusion The GC-MS/MS analytical method for the analysis of ephedrine and pseudoephedrine components in urine established in this study is accurate,stable and sensitive,which can provide data technical support for the forensic toxicological analysis of amphetamine-type drugs or new psychoactive substances in the cathinone group.

Freeze-drying technique,also known as lyophilization,is a process of removing moisture from a solution or suspension through freezing and vacuum dehydration to maintain the stability of the samples and prolong their shelf life.Freeze-drying technology has been widely used in food,pharmaceutical,clinical testing,chemical and other fields but its application in the field of forensic medicine has just started.Polymerase chain reaction(PCR)and its derivative detection technologies are widely used in forensic DNA detection,but PCR reagents need to be stored and transported at low temperature.In recent years,forensic scientists have begun applying freeze-drying technology to PCR amplification reagents to solve the transportation and storage problems of PCR reagents.In order to promote the application of PCR freeze-drying technology in forensic genetics,this paper mainly expounds the research course,system and process of PCR freeze-drying technology,compares the advantages and disadvantages of PCR reagents with traditional PCR reagents,and introduces the advantages and challenges of PCR freeze-drying reagents in forensic medicine.

Sampling is the first stage of the DNA Typing in forensic science,and some studies found that the sampling technology affected the outcomes of"Contact DNA"testing.Since swabs are the most commonly used collection instrument for"Contact DNA",the researchers in forensic science field should pay more attention to study the collection efficiency of swabs.However,currently the majority of relevant research is focused on downstream testing processes,such as typing and amplification;the corresponding work on sampling performance by swabs is quite limited.Furthermore,the absence of an internationally recognized standard procedure makes it impossible to directly compare the collection results among laboratories.In this paper,a review on the use of swabs in the forensic science field is presented.It analyzes the collection efficiency,advantages and disadvantages of different swabs,and investigates the need and feasibility of developing a standardized method to evaluate the swab collection efficiency,for improving the sampling performance of swabs and ultimately increasing the detection rate of"Contact DNA"in forensic science.

Objective To verify the accuracy of the"manual tracing+summation method"for calculating the area of subcap aponeurotic hematoma using CT images in the practice of judicial expertise.Methods Subcap aponeurotic hematoma at different locations were simulated using"skull+colored clay plastic"model.The simulated hematoma areas were calculated via RadiAnt DICOM Viewer(64-bit)after CT scanning and compared with manual measurements.Results(1)For completely scaned simulated hematoma,the area of manual calculation is smaller than that measured by the expert assistance system for human injury identification,yet demonstrated relatively high accuracy;(2)Scanning planes parallel to the three scan baselines has the greatest impact on the imaging of top hematoma,often leading to incomplete scanning of both the top of the skull and hematoma.Conclusion When the scan of hematoma is complete,the subcap aponeurotic hematoma calculated by manual tracing is close to true values.However,incomplete scans may lead to disputable results and time-consuming and laborious manual calculations.In view of the current situation,pixel level semantic segmentation technology in the field of computer vision can be combined with the application of level set,gray reconstruction and other segmentation algorithms to obtain the three-dimensional outline of the hematoma area,so as to calculate the hematoma area and provide the most direct data analysis for judicial identification.