Gunpowder particles as a factor in a gunshot from up close

Existence of different opinions on the role of gunpowder particles in determining close shot distance promoted the experiments with pistol "PM" and sporting fowling piece in vertical and horizontal directions at different distances from 0.5 up to 2.5 m using targets made of pasteboard and moistened photographic paper. The quantities of gunpowder particles on the targets which were calculated by stereoscopic microscope increased distinctly in vertical shot direction (from above downwards), especially at distances 2 and 2.5 m and particle flight distance rose; in horizontal shot direction distances of gunpowder particle flight didn't exceed 2-3 m.     

Frequency of bone lesions: an inadequate criterion for gunshot wound diagnosis in skeletal remains

A retrospective study was carried out on 130 fatalities due to gunshot wounds to determine whether the combined absence of bone damage and projectile in a skeleton is sufficient to eliminate a diagnosis of gunshot wound. Our findings showed that bone lesions were present in about 90% of the cases and were associated with intracorporeal projectile(s) in about 70% of the cases. The presence or absence of bone lesions seemed independent of the gun characteristics, the shot conditions, and the type of death. The cause of death was predominantly brain injury in cases with bone lesions whereas thoracic, abdominal, and peripheral vascular causes were more frequently encountered in cases without bone damage. We concluded that the combined absence of bone lesions and intracorporeal projectile (about 5% in our series) cannot exclude a diagnosis of death secondary to gunshot wounds.     

Handguns and ammunitions indicators extracted from the GSR analysis

The computer automated scanning electron microscope. X-ray microanalysis of Firearms Discharge Residue (FDR) can reveal substantial information about the circumstances of their generation beyond the presence of characteristic gunshot residue (GSR). Indicators of the type of weapon and ammunition used can he obtained from the distribution of GSR particle shapes and from the multi-element analysis of the FDR sample. This is demonstrated for a large database of GSR samples from nine different handguns and over 60 different ammunitions. An example classification scheme is presented for the supporting particles generally found present in FDR. When particle type area concentration ratios are normalized to the iron (Fe) particle type, results show it is possible to distinguish much about the metal used in the weapon manufacture, whether it was of large or small caliber, whether the bullets were jacketed or plated, and whether the cartridge cases were of aluminum, brass, or nickel-plated brass. Standardization of such analytical schemes would be advantageous.     

Rapid search and quantitative analysis of gunshot residue particles in the SEM

Automated scanning electron microscopy coupled with image analysis and X-ray micro analysis was used to characterize a variety of gunshot residue (GSR) samples. More than 500 rounds of commercially available ammunition and six different types of hand gulls were used in the study of 17 GSR and 19 reference specimens. The individual particle X-ray composition was determined for 12 different elements. Elemental composition of GSR particles was highly variable but consistent with compounds mixed into or associated with a barium oxide matrix. When present in a specimen, GSR could be adequately characterized with automated procedures in less than an hour by restricting analyses to features larger than 2 microm. In "clean" samples, a higher resolution particle search was required to avoid reporting false negatives. Careful control of the back scattered electron signal strength threshold, by reference to a standard, was needed to ensure both time-efficient and accurate analyses. Samples collected from non-shooting subjects. active in a physical environment which contained firearms discharge residue were seen to be easily contaminated by sub-micron GSR particles.     

A preliminary investigation into the use of FTIR microscopy as a probe for the identification of bullet entrance holes and the distance of firing

FTIR spectroscopy has been found to be a valuable probe for the analysis of the distribution of organic components such as nitroglycerine in gunshot residues deposited on and around the bullet entrance hole of the clothing of the victim in short range firearm discharges. The method can be utilised for the detection and estimation of organic gunshot residues (OGSR) on the hands and clothing of the shooter. The method is specific and sensitive and is likely to be free from interference from, for example, environmental pollution. The method shows potential to be utilised as a suitable alternative to the widely used SEM-EDX analysis of the total contents of lead, barium and antimony present in the gunshot deposits around the bullet entrance hole. The method was tested in the laboratory and the results were validated by Gas Chromatography-Mass Spectrometry (GC-MS).     

Gunshot residue particle velocity and deceleration

The velocity of over 800 gunshot residue particles from eight different sources was determined using high speed stroboscopic photography (spark gap light source). These particles were found to have an average velocity of 500 to 600 ft per second. Many particles acquired considerably higher velocities. Thus, the particles have sufficient energy to embed themselves within certain nearby targets like skin or fabric. The relatively high velocity that the particles acquire explain the formation of stippling on skin in close proximity to a muzzle discharge. These findings also indicate little influence of air currents on particle behavior near the muzzle. The deceleration of less than 100 particles during a 100-microsecond interval was also calculated. The particles experienced rapid rates of deceleration which would explain why few particles are found in test firings beyond 3 ft from the muzzle of a discharged firearm. Because of their relatively high velocity, normal wind velocity would not be expected to significantly influence their motion near the muzzle.     

Trends in Officer‐involved Firearm Deaths in Oklahoma from 2000 to 2015

The purpose of this study was to collect data and disseminate trends in officer‐involved firearm deaths in Oklahoma from 2000 to 2015. The Oklahoma Office of the Chief Medical Examiner (OCME) database was searched for civilian decedents with gunshot wounds inflicted by law enforcement officers and officer decedents with gunshot wounds inflicted by civilians. Five decedents were law enforcement officers, while 274 decedents were civilians. The number of civilian decedents throughout the study followed a quadratic trend. Civilian decedents were most commonly males (95%) between the ages of 20 and 39 (64%), had one or two gunshot wounds (46%), and had an increasing number of gunshot wounds over time. Postmortem toxicology testing most commonly detected ethanol, methamphetamine, cocaine, and PCP. Efforts toward increased tracking by various agencies and more scientific studies like this are needed to facilitate future analysis of trends in officer‐involved firearm deaths.     

Gunshot residue testing in suicides: Part I: Analysis by scanning electron microscopy with energy-dispersive X-ray

Several different methods can be employed to test for gunshot residue (GSR) on a deceased person's hands, including scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM-EDX) and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Each of these techniques has been extensively studied, especially on living individuals. The current studies (Part I and Part II) were designed to compare the use and utility of the different GSR testing techniques in a medical examiner setting. In Part I, the hands of deceased persons who died from undisputed suicidal handgun wounds were tested for GSR by SEM-EDX over a 4-year period. A total of 116 cases were studied and analyzed for caliber of weapon, proximity of wound, and results of GSR testing, including spatial deposition upon the hands. It was found that in only 50% of cases with a known self-inflicted gunshot wound was SEM-EDX positive for at least 1 specific particle for GSR. In 18% of the cases there was a discernible pattern (spatial distribution) of the particles on the hand such that the manner in which the weapon was held could be determined. Since only 50% of cases where the person is known to have fired a weapon immediately prior to death were positive for GSR by SEM-EDX, this test should not be relied upon to determine whether a deceased individual has discharged a firearm. Furthermore, in only 18% of cases was a discernible pattern present indicating how the firearm was held. The low sensitivity, along with the low percentage of cases with a discernible pattern, limits the usefulness of GSR test results by SEM-EDX in differentiating self-inflicted from non-self-inflicted wounds.     

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.     

Effects of Decomposition on Gunshot Wound Characteristics: Under Cold Temperatures with No Insect Activity

Abstract:  Information on gunshot wound characteristics has been well documented; however, there is little documented information on the effects of decomposition or environmental conditions on gunshot wound characteristics. This study was conducted in order to determine if decomposition would obscure or alter the physical surface characteristics of gunshot wounds when exposed to a low temperature environment. The study was conducted from November 2005 to January 2006 in Nova Scotia, Canada in forested and exposed environments, with air temperatures between −10°C and +10°C. Pigs were used as human models and were shot six times each at three different ranges (contact, 2.5 cm, and 1.5 m). Gunshot wound characteristics persisted until the wounds were covered with ice and snow, after which changes were observed. The changes were recognized as being unique to the different ranges of gunshots and it was concluded that changes due to decomposition under the conditions tested would not affect the collection and interpretation of gunshot wound evidence.     

Image analysis of gunshot residue on entry wounds. II--A statistical estimation of firing range.

A statistical investigation of the relationship between firing range and the amount and distribution of gunshot residue (GSR), used automated image analysis (IA) to quantify GSR deposit resulting from firings into pig skin, from distances ranging between contact and 45 cm. Overall, for a Ruger .22 semi-automatic rifle using CCI solid point, high velocity ammunition, the total area of GSR deposit on the skin sections decreased in a non-linear fashion with firing range. More specifically there were significant differences in the amount of GSR deposited from shots fired at contact compared with shots fired from distances between 2.5 and 45 cm; and between shots fired from a distance of 20 cm or less, with shots fired at a distance of 30 cm or more. In addition, GSR particles were heavily concentrated in the wound tract only for contact and close range shots at 2.5 cm, while the particle distribution was more uniform between the wound tract and the skin surfaces for shots fired from distances greater than 2.5 cm. Consequently, for future scientific investigations of gunshot fatalities, once standards have been established for the weapon and ammunition type in question, image analysis quantification of GSR deposited in and around the gunshot wound may be capable of providing a reliable, statistical basis for estimating firing range.     

A Study of the Presence of Gunshot Residue in Pittsburgh Police Stations using SEM/EDS and LC‐MS/MS

Due to possible secondary transfer of gunshot residue (GSR) onto a suspect in police custody prior to sampling, a baseline must be created for the amount of GSR present. With an increase of “lead free” ammunition, testing for both gunpowder and primer GSR is relevant. Seventy samples were collected using carbon‐coated adhesive stubs from four Pittsburgh Police Stations and vehicles to investigate these locations as sources of secondary GSR contamination. These seventy samples were analyzed for primer GSR using scanning electron microscopy‐energy‐dispersive X‐ray spectrometry. One primer GSR particle was detected; no sample was classified as positive for primer GSR. These same samples were then analyzed for gunpowder GSR using liquid chromatography coupled to tandem mass spectrometry to test for akardite II, ethylcentralite, diphenylamine, N‐nitrosodiphenylamine, 2‐nitrodiphenylamine, and 4‐nitrodiphenylamine. Ethylcentralite was quantifiable in two test samples. These results suggest there is a negligible potential for secondary transfer of primer and gunpowder GSR.     

Image analysis of gunshot residue on entry wounds: II – A statistical estimation of firing range

A statistical investigation of the relationship between firing range and the amount and distribution of gunshot residue (GSR), used automated image analysis (IA) to quantify GSR deposit resulting from firings into pig skin, from distances ranging between contact and 45 cm. Overall, for a Ruger .22 semi-automatic rifle using CCI solid point, high velocity ammunition, the total area of GSR deposit on the skin sections decreased in a non-linear fashion with firing range. More specifically there were significant differences in the amount of GSR deposited from shots fired at contact compared with shots fired from distances between 2.5 and 45 cm; and between shots fired from a distance of 20 cm or less, with shots fired at a distance of 30 cm or more. In addition, GSR particles were heavily concentrated in the wound tract only for contact and close range shots at 2.5 cm, while the particle distribution was more uniform between the wound tract and the skin surfaces for shots fired from distances greater than 2.5 cm. Consequently, for future scientific investigations of gunshot fatalities, once standards have been established for the weapon and ammunition type in question, image analysis quantification of GSR deposited in and around the gunshot wound may be capable of providing a reliable, statistical basis for estimating firing range.     

Distribution of lead and barium in gunshot residue particles derived from 0.22 caliber rimfire ammunition.

0.22 caliber rimfire ammunition is commonly encountered in firearms incidents in Australia. This paper reports on work which has confirmed the nonhomogeneous nature of gunshot residue (GSR) particles and that the lead and barium distribution within particles varies significantly with the particle size and structure. The outcome has been an improved understanding of how the particle formation influences the ability to determine the origin of GSR derived specifically from 0.22 caliber rim fire ammunition.     

Effects of Decomposition on Gunshot Wound Characteristics: Under Moderate Temperatures with Insect Activity

Abstract:  Previous studies document characteristics of gunshot wounds shortly after they were inflicted. This study was conducted to determine if the early stages of decomposition obscure or alter the physical surface characteristics of gunshot wounds, thereby affecting the quantity and quality of information retrievable from such evidence. The study was conducted in August and September, 2005 in Nova Scotia, Canada in forested and exposed environments. Recently killed pigs were used as research models and were shot six times each at three different ranges (contact, 2.5 cm, and 1.5 m). Under these test conditions, the gunshot wounds maintained the characteristics unique to each gunshot range and changes that occurred during decomposition were not critical to the interpretation of the evidence. It was concluded that changes due to decomposition under the conditions tested would not affect the collection and interpretation of gunshot wound evidence until the skin was degraded in the late active or advanced decay stage of decomposition.     

Automated gunshot residue particle search and characterization

The main disadvantage to gunshot residue (GSR) particle analysis utilizing scanning electron microscope/energy dispersive X-ray (SEM/EDX) instrumentation has been the excessive operator time required for search and identification. This study uses an automated particle search and characterization program for unattended GSR search and identification. This system allows for automatic matrix search, particle sizing, chemical typing, and spectral aquisition with subsequent storage of data to disk for later operator review and verification. This work describes various aspects of the program, determines appropriate parameters adequate for both unique and characteristic GSR particle identification, and evaluates the reliability of data obtained. Samples are collected via the tape lift method from test-firings of .38, .32, .25, and .22 caliber handguns at time after firing intervals of 0 to 6 h. Unique GSR particles are consistently and correctly identified by this method on tape lift samples taken up to 4 h after firing. False positive results of unique GSR particles are not encountered on control handblank samples. This technique appears to provide the forensic science community with an operator-free method of reliable GSR particle search and an improved analyst-time-per-case ratio.     

92式手枪射入口形态特征与射击距离的关系

目的研究手枪射入口形态特征与射击距离的关系,为射击距离的推断提供依据。方法选择92式手枪,在带皮的猪肉上覆盖白色棉布,设计了0m,0.1m,0.2m,0.5m1.0m,1.5m,3.0m,5.0m,10m,15.0m,20.0m,25.0m共12个射击距离,对白棉布和肉皮上的弹孔进行拍照,对比研究不同射击距离的射入口形态特征,并利用Autocad软件对射入口的面积进行计算。结果白棉布和肉皮上射入口的形态特征与射击距离有一定的相关性。结论根据射入口的形态特征,能够对射击距离进行推断,对涉枪案件中射击距离的判断有参考价值。     

The case of the missing victims: Gunshot woundings in the National Crime Survey

National Crime Survey (NCS) data yield an estimate that 171,000 Americans were nonfatally shot in criminal assaults, robberies, and rapes for the period 1973–1979. Comparing this estimate with the number of firearms homicides during this period suggests either that the death rate in gunshot cases is very high (over 1/3) or that the NCS estimate is low. Based on police-generated data appropriate to estimating the true death rate from gunshot wounds, it appears that the NCS estimate is low by a factor of about 3.0 compared with the number of criminal gunshot woundings known to the police. It is common knowledge that survey-based estimates of assault rates tend to be relatively unreliable, a fact that has been attributed to problems with respondents being willing and able to recall threats, fist fights, and other minor assaults. The current result indicates that the estimation problem is not limited to minor assaults. There is reason to think that the underestimate of gunshot woundings is the result of problems with the NCS sample as well as problems with respondent cooperation.     

Gunshot residue patterns on skin in angled contact and near contact gunshot wounds

The goal of this study was the reproduction of shape and pattern of gunshot residues in near contact and contact gunshot wounds by a series of experimental gunshots on a skin and soft tissue model. The aim was to investigate the shape and direction of soot deposits with regard to the muzzle according to different muzzle-target angles, firing distances, type of ammunition and weapon and barrel length. Based on a review of the literature and on the results of the experiments the authors could make the following statements of gunshot residues in angled contact and close contact gunshot: (1) gunshot residues on the target surface can be differentiated in a "inner" and "outer powder soot zone"; (2) the outer powder soot zone is much less visible than the inner powder soot zone and may lack on human skin; (3) with increasing muzzle target distance both inner and outer powder soot halo increase in size and decrease in density; (4) in angled shots the inner powder soot halo shows an eccentric, elliptic shape which points towards the muzzle, regardless of ammunition, calibre and barrel length; (5) the outer powder soot points away from the muzzle in angled contact and close contact shots.     

带消音器枪弹创的实验病理研究

使用国产7．62mm口径微声轻型冲锋枪，以不同距离射击实验动物，制成带消音器枪弹创，并使用国产7．62mm口径轻型冲锋枪作对照进行对比观察。结果表明：在接触和近距离射击时，带消音器枪弹刻与典型枪弹剑比较有明显不同；根据消音器的结构和原理，结合实验结果，建立了带消音器枪弹创的形态学特征及其诊断依据。为法医学检验鉴定提供了实验性资料。