Estimation of explosive charge mass used for explosions on concrete surface for the forensic purpose

The method of choice used by most terrorists for achieving political goals remains the utilization of explosive devices and there is always visible evidence at a crime scene after the deployment of such devices. Given favorable circumstances, forensic analysis can determine the cause of the explosion — the type of the explosive device, the means of detonation, the type and mass of the explosive charge that has been used and perhaps provide information to lead to the identity of the individual who may have constructed or deployed the explosive device, etc. Evidence of an explosion may take the form of a crater or other damage which may provide some information facilitating and estimating the mass of explosive material used. This paper reports the findings obtained by performing experimental explosions of known charges on a concrete surface, in order to establish the correlation between the charge weight and the effects of the explosion. Known masses of explosives were fired and the dimensions of craters made by explosions were measured. Five empirical equations for estimation of the explosive charge mass from crater dimensions were used.     

Explosion Scene Forensic Image Interpretation

Image interpretation is an important aspect in the field of forensic science; however, it is seldom reported how to use these techniques in explosion scene forensic investigations. On 12 August 2015, a series of explosions killed 165 people and injured hundreds more at a container storage station at the Port of Tianjin. In this study, we applied image interpretation methods to determine the seat of the explosion by analyzing low‐quality video clips of the event. The interpretation fits well with recently published standard operating procedures, including the hypothesis, evaluation, inference, and confirmation. Image processing was adopted to enhance the images while the explosion scene was reconstructed with the same images. Some important features were extracted and utilized to distinguish whether the flashes were caused by reflection or a real blast. We reveal the real explosion location, which guides the overall investigation. The results indicate that image interpretation is a powerful tool for forensic investigators to analyze low‐quality images in complicated explosions or fire accidents.     

Lead-free primer residues: a qualitative characterization of Winchester WinClean, Remington/UMC LeadLess, Federal BallistiClean, and Speer Lawman CleanFire handgun ammunition

The elemental composition and postfiring residues of several "lead-free" or "nontoxic" centerfire handgun ammunition types currently available to the general public were examined. Offerings from Winchester, Remington/UMC, Federal and Speer were obtained from retail sources in both .45 ACP and 9 mm when possible. A total of 112 postfiring residue samples (SEM pins) were collected at varying distances from the muzzle, at two distances from target and from the shooter's hands. An additional 20 samples were collected by direct ignition of primers. Qualitative determinations were carried out using scanning electron microscopy (SEM)/electron dispersive spectrometry (EDS) analysis. All types tested contained aluminum (Al), silicon (Si), copper (Cu), and zinc (Zn). Most contain traces of sulfur and calcium. Winchester WinClean and Remington LeadLess contained potassium as the principle ingredient. Federal BallistClean contained barium, while Speer Lawman CleanFire contained strontium. In the main, these compared favorably with manufacturers' MSDS publications and patents granted. The characterizations undertaken here will be of use to the forensic electron microscopist as these formulations gain popularity.     

Independence day explosion on lovers key

The display of fireworks is a popular holiday celebration in the United States. Because injuries due to recreational fireworks-related explosions among private consumers are relatively common, the sale of fireworks is regulated by the federal government and is also limited by state and local laws. In contrast, because fireworks display companies are under tight safety regulations, explosions in the professional pyrotechnics industry are uncommon occurrences, and the literature contains rare reports of injuries and fatalities resulting from such explosions. We report the 2003 Fourth of July commercial fireworks explosion on Lovers Key in southwest Florida that resulted in five fatalities. Events occurring during the investigation of the scene of this explosion illustrate the unique considerations and hazards for medicolegal death investigators, law enforcement and other investigative agencies. Additionally, this case demonstrates unusual aspects of the postmortem examinations performed on victims of fireworks-related incidents.     

Heat Induced Changes to Dental Resin Composites: A Reference in Forensic Investigations?*

The objective was to investigate color change and surface damage in dental resin composites exposed to high temperatures over different time intervals for comparative purposes. Samples were prepared using two resins - Z100(R) (R1) and Charisma (R2), heated at the following temperatures: 200 degrees C, 400 degrees C, 600 degrees C, 1000 degrees C, for 15, 30 and 45 min (n = 104 for each resin sample). Color (DeltaE) and brightness (DeltaL) changes were analyzed by spectrophotometry using the CIE Lab system and surface changes by Scanning Electron Microscopy (SEM). R1 showed more intense color changes after heat exposure than R2. DeltaL values were found to be the best parameter for evaluation of light and color change. A biphasic pattern after thermal exposure was detected, from dark brown to light white. SEM showed more intense alterations in R2 than in R1. These results indicate that the parameters observed in both resins are useful as a guide in forensic analyses.     

Damage caused to fibres by vapour cloud explosions

Research on the very specific damage to single textile fibres caused by vapour cloud explosions is presented. Vapour cloud explosion experiments were carried out using a selection of 41 garments differing in colour, fibre composition and textile construction. Fibres subjected to a vapour cloud explosion become wider at the end, often taking the form of a ball, bulb or shovel, while the morphological structure of the remaining part of the fibre remains almost unchanged. The presented results can clearly indicate that an explosion took place at the scene of the crime. The authors would like to be able to provide investigators with specific information on how to link clothes (and thus people) to a specific type of crime.     

The Effect of Skin Debris on Gunshot Residue Sampling and Detection

These experiments were designed to determine whether skin debris (desquamated epithelial cells and apparent skin oils) affects gunshot residue (GSR) particle detection on the sticky tape lift samples prepared for scanning electron microscopy (SEM). A dabbing experiment showed that GSR particles accumulate not only on the adhesive surface of the sampler, but also on the epithelial cell surfaces. Samplers were loaded with target GSR followed by dabbing 30 times on the back of a hand. Backscatter electron images were taken at 20 kV and for some at 30 kV of the same areas. The samplers were then treated with a sodium/calcium hypochlorite solution (bleach) to remove skin debris and again imaged in the SEM. Comparison of these images shows more GSR particles will likely be revealed at 30 kV than 20 kV and more particles revealed by the bleach treatment in an automated SEM system.     

Aerosol or IED explosion: a case report

The Punjab State has witnessed quite a large number of explosions caused by terrorists for more than one and half decades. Conseqently, any incident of an explosion in the state gives the impression of having resulted from terrorist activity. The authors examined the scene of occurrences and carried out laboratory examinations. The quantitative estimation of the aerosol mixture formed from the LPG leaked from the cylinder and the volume of space available is within the critical limits of explosive forming mixture, has substantiated the explosion due to the leakage of LPG.     

Postmortem findings in 22 victims due to two grain silo explosions in France

In 1982 and 1997 there were explosions of barley-containing silos in France, one in Metz (1982) and the other in Blaye (1997). There were a total of 25 victims, including 23 fatalities (12 in Metz and 11 in Blaye). In each case there was one survivor. This report is a retrospective study of 22 victims (11 at each site); all of them had multiple lesions due to the explosion and the immediate aftermath. The lesions demonstrated direct involvement of the blast effect associated with silo destruction, the heat from the explosion, the effects of toxic gases and asphyxia. The forensic pathologist is an important member of the emergency response team. This team has the responsibility for initially assessing the damage and for identifying the victims. The role of the forensic pathologist is therefore essential and they should be included in emergency planning to facilitate the initial assessment, shorten the time taken to identify the victims and improve safety procedures. Although dust explosions in agro-business plants are occurring more frequently, postmortem data are rare.     

微波消解-扫描电镜联用法在溺死诊断中的应用

目的探讨微波消解-扫描电镜联用法在溺死诊断中的应用价值。方法收集已知死因的尸体标本105例,其中水中尸体85例(生前溺死70例,死后抛尸入水15例),陆地自然死亡尸体20例。水中死亡案例同时收集落水处水样。分别用微波消解-扫描电镜联用法(方法 A)和硝酸破机-光镜联用法(方法 B)对上述尸体的离体肺、肝、肾、骨髓组织及水样进行硅藻定性、定量检测。结果①溺死尸体的肺、肝、肾、骨髓中及落水处水样硅藻检出率:A法分别为100%、94.3%、92.9%、82.9%、100%,硅藻检验阳性率为100%;B法分别为90%、62.9%、51.4%、28.6%、92.9%,硅藻检验阳性率为65.7%。②两种方法检出的硅藻种类与落水处水样中硅藻的种类均一致。③两种方法在死后入水尸体离体的肺中也检出少量硅藻(<3个/2g肺组织),但在死后入水尸体的其它脏器及陆地自然死亡尸体脏器中均未检出硅藻。结论微波消解-扫描电镜联用法较硝酸破机-光镜联用法对尸体离体组织脏器中的硅藻检出率高,方法灵敏,定性准确。     

The transference of patterns printed or indented on a sheet of paper to a plastic surface

Experiments have been made in which the image of Xerox-letters printed on a sheet of paper is transferred to a sheet of plastic and developed by dusting. The sheet of paper is sandwiched between two sheets of plastic, which are pressed between two flat metal plates by a mechanical press. After removing the pressure, the sheet of plastic facing the letter-printed surface of the sheet of paper is separated or torn from the paper using electrically insulated forceps. Then by sifting fine alumina powder onto the plastic surface, a dust figure can be obtained. This figure shows the transcribed letters corresponding to the original Xerox-letter on the sheet of paper.By this method, indented letters, or letters drawn with ink on a sheet of paper, or a fingerprint impressed on a sheet of paper can be transcribed onto the surface of a sheet of plastic.     

Ballistic characterization of the Remington Premier Copper Solid sabot shotgun slug

We evaluated the impact and penetration characteristics of the Remington Copper Solid sabot shotgun slug with standardized ballistic tests and used this information to predict tissue wounding patterns. This unique ammunition, first distributed in 1993, is composed of a solid copper, hollow-point slug with longitudinal slots cut into the nose. The slug is fitted into a hard plastic sabot with 8 finger-like projections and loaded into a shotgun shell with two plastic wads separating it from the underlying gunpowder charge. The ammunition was fired through a 12-gage shotgun using a rifled barrel, a smooth-bore barrel with rifled choke, and a smooth-bore barrel with a smooth modified choke into targets consisting of poster board and 10% ballistic gelatin at a variety of distances. The copper slug and plastic sabot created single 8-fingered asterisk-shaped defects in the poster board when fired at distances of less than 7 to 9 ft (approximately 2 to 3 m). All three barrel types performed similarly. At greater distances, the sabot impacted the targets separately from the slugs and created variably shaped defects that reflected base-first, nose-first, and side-first impacts. Increasing muzzle-to-target distances generally increased the impact distances between the slug and sabot. There was no predictable relationship between the sabot and slug impact points for any of the three barrel types. With each barrel tested, the wads created separate defects from the slug at distances greater than 5 ft (1.5 m). The distances between the slug and the wad impact points increased with increasing muzzle-to-target distances up to 40 ft (12 m), after which the wads generally no longer struck the targets. The slug created atypical defects at distances between 7 and 150 ft (approximately 2 to 45 m), probably due to yawing or tumbling. When the slug impacted the gelatin block in a nose-first orientation, the slotted nose portion tended to fragment and radially deposit pieces in the gelatin that were visible on radiographs. When the slug struck the gelatin target in a side-first orientation, it passed through the gelatin intact. The slug, sabot, and wads of this unique projectile separate and create independent impact points in a stereotypical manner independent of barrel type. This pattern of separation allows estimates to be made of ranges of fire. Wounds created in human tissues by this ammunition would likely have similar asterisk-shaped configurations, and nose fragments may be deposited in tissues and seen radiographically. Rectangular wounds created by the tumbling or yawing slug might be mistaken for intermediate target wounds.     

Pyrotechnic reaction residue particle analysis

Pyrotechnic reaction residue particle (PRRP) production, sampling and analysis are all very similar to that for primer gunshot residue. In both cases, the preferred method of analysis uses scanning electron microscopy to locate suspect particles and then uses energy dispersive x-ray spectroscopy to characterize the particle's constituent chemical elements. There are relatively few times when standard micro-analytical chemistry performed on pyrotechnic residues may not provide sufficient information for forensic investigators. However, on those occasions, PRRP analysis provides a greatly improved ability to discriminate between materials of pyrotechnic origin and other unrelated substances also present. The greater specificity of PRRP analysis is the result of its analyzing a large number of individual micron-sized particles, rather than producing only a single integrated result such as produced using standard micro-analytical chemistry. For example, PRRP analyses are used to demonstrate its ability to successfully (1) discriminate between pyrotechnic residues and unrelated background contamination, (2) identify that two different pyrotechnic compositions had previously been exploded within the same device, and (3) establish the chronology of an incident involving two separate and closely occurring explosions.     

Characterization of pyrotechnic reaction residue particles by SEM/EDS

Today the method commonly used for detecting gunshot residue is through the combined use of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). In recent years, this same methodology began to find use in detecting and characterizing pyrotechnic reaction residue (PRR) particles whether produced by explosion or burning. This is accomplished by collecting particulate samples from a surface in the immediate area of the pyrotechnic reaction. Suspect PRR particles are identified by their morphology (typically 1 to 20 microm spheroidal particles) using an SEM; then they are analyzed for the elements they contain using X-ray EDS. This can help to identify the general type of pyrotechnic composition involved.     

Development and validation of a liquid chromatography-mass spectrometry assay for hair analysis of methylphenidate

Examination of various SIM cards and smart card devices indicates that data may be retained in SIM card memory structures even after heating to temperatures up to 450 degrees C, which the National Institute of Standards and Technology (NIST) has determined to be approximately the maximum average sustained temperature at desk height in a house fire. However, in many cases, and certainly for temperatures greater than 450 degrees C, the SIM card chip has suffered structural or mechanical damage that renders simple probing or rewiring ineffective. Nevertheless, this has not necessarily affected the data, which is stored as charge in floating gates, and alternative methods for directly accessing the stored charge may be applicable.     

同卵双生子外周血DNA甲基化谱的差异

目的通过比较不同个体外周血DNA甲基化谱的差异,评估DNA甲基化在同卵双生子个体甄别中的应用价值。方法在知情同意基础上获得22对同卵双生子外周血样。抽提基因组DNA后进行重亚硫酸盐转化．采用Illuraina公司的人27k甲基化微珠芯片检测基因组27578个CpG位点的甲基化程度（启值）。依据常染色体CpG位点的序值,采用欧氏距离计算方法计算同卵双生子间以及同性男ll的无关个体间的表观遗传距离。比较同卵双生子对与无关个体对两组不同人群间的表观遗传距离差异。结果同卵双生子对人群以及无关个体对人群中的男性个体对与女性个体对的表观遗传距离差异均无统计学意义（P值分别为0．0695和0．4825）。同卵双生子对的表观遗传距离显著低于无关个体对人群（中位数：6．02νs7．20,P=0．0002）．但两组人群的表观遗传距离均显著大于4．00（P〈0．0001）。结论同卵双生子间的外周血DNA甲基化谱差异显著．DNA甲基化是进行同卵双生子个体甄别的有效生物学标记。     

GSR2005—Continuity of the ENFSI Proficiency Test on Identification of GSR by SEM/EDX

Abstract:  Within the framework of the ENFSI Expert Working Group "Firearms" a proficiency test on the detection and identification of GSR by energy-dispersive scanning electron microanalysis (SEM/EDX) is carried out in a 2 years term. The latest test was performed in 2005/2006 and was denoted as GSR2005 . Seventy-five laboratories from 28 countries participated in this proficiency test and submitted in total 83 independent data-sets. The participating laboratories were requested to determine the total number of PbSbBa containing particles on a synthetic test sample following their own laboratory specific methods of automated GSR particle search and detection by SEM/EDX. Furthermore size and position of the detected particles had to be reported by the laboratories and were evaluated statistically. The results were compiled by means of z -scores according to the IUPAC and EURACHEM guidelines—assessing individual laboratory achievements (inter-laboratory) as well as intra-laboratory performance—and were compared to the results of the previous proficiency test run GSR2003 ( 1 ). The comparison shows that there is a noticeable improvement in the method's detection capability.     

Frozen human bone: a microscopic investigation

The taphonomic effects of prolonged extreme cold and freezing on human bone have received little research attention. Questions of specific interest include whether previously frozen bone can be identified and whether freezing alters the structural integrity enough to prevent histological aging. There is no evidence from previous studies that freezing damages the structural integrity, and to date no research investigating the freezing process on bone microstructure has been undertaken. This research attempts to distinguish histologically previously frozen bone from nonfrozen bone by identifying patterned defects. To determine the effects of freezing in bone microstructure using light and scanning electron microscopy (SEM), several human bone sections were subjected to prolonged freezing and allowed to thaw before thin sectioning. Light microscopy failed to demonstrate statistically significant differences between frozen and nonfrozen specimens. SEM analysis revealed fractures, although these lacked pattern and did not occur systematically throughout the section. Evidence of microstructural changes caused by liquid expansion, however, was remarkable but did not alter the structural integrity of the microstructure. The results of this study suggest that freezing does not alter the process of histomorphological analysis.     

Identification of gunshot residue: a critical review

A review of the scientific papers published on inorganic gunshot residue (GSR) analysis permits to study how the particle analysis has shown its capability in detection and identification of gunshot residue. The scanning electron microscope can be the most powerful tool for forensic scientists to determine the proximity to a discharging firearm and/or the contact with a surface exposed to GSR. Particle analysis can identify individual gunshot residue particles through both morphological and elemental characteristics. When particles are detected on the collected sample, the analytical results can be interpreted following rules of a formal general interpretative system, to determine whether they come from the explosion of a primer or from other possible sources. The particles on the sample are compared with an abstract idea of "unique" GSR particle produced by the sole source of the explosion of a primer. "Uniqueness" is not the only problem related to GSR detection and identification for a forensic scientist. With "not-unique" particles interpretation of results is extremely important. The evidential strength of "not-unique" particles can increase with a more fruitful interpretative framework based on Bayes rule. For the assessment of the value of a GSR in linking a suspect and a crime, it is important to compare two hypothesis: the first can be that of the evidence if the suspect has been shooting in a specific situation, the second that of the evidence if the suspect was not involved in this shooting. This case specific or case-by-case approach is closer to what the court is interested in. The authors consider that a "case-by-case" approach should be followed whenever possible. Research of models and data such as those developed in other trace evidence material (fibres, glass, etc.) using a Bayesian approach is suggested in the interpretation of GSR.     

扫描电镜/X射线能谱仪检验电流斑规范化方法探讨

目的探讨电流斑皮肤金属化的机理、检材提取处理和扫描电镜/能谱仪检验规范化方法,对检验结果进行分析和价值判断。方法用扫描电镜/能谱检验,采用低倍大窗口覆盖损伤区域采集平均元素能谱图,并在可能的金属元素富集区域寻找球形金属颗粒。结果扫描电镜下可观察到散在的孔穴、细胞碎屑、龟裂、裂隙等特征,有些电流斑可检出金属元素,其中部分电流斑可发现球形金属颗粒。结论采用规范化的检材提取、处理和检验方法可消除随意性方法造成错检的可能。电流斑皮肤上异常含量的金属附着可支持病理检验符合电流斑表现的结论,同时也为电击导体的推断和金属元素成分比对提供依据。球形金属颗粒的发现揭示存在电弧高温的可能性极大,可强力支持病理检验符合电流斑表现的结论。