Secondary transfer of organic gunshot residues: Empirical data to assist the evaluation of three scenarios

The present study aimed at providing data to assess the secondary transfer of organic gunshot residues (OGSR). Three scenarios were evaluated in controlled conditions, namely displacing a firearm from point A to point B, a simple handshake and an arrest involving handcuffing on the ground. Specimens were collected from the firearm, the hands of the shooter and the non-shooter undergoing the secondary transfer in order to compare the amounts detected.Secondary transfer was observed for the three scenarios, but to a different extent. It was found that displacing a firearm resulted in secondary transfer in <50% of the experiments. The firearm also had an influence, as contrary to the pistol, no secondary OGSR were detected using the revolver. Shaking the hand of the shooter also transferred OGSR to the non-shooter's hand. In that case, the amount of OGSR was generally higher on the shooter than on the non-shooter. Finally, the largest secondary transfer was observed after the arrest with handcuffing with positive results in all cases using the pistol. In that scenario, the amounts on the shooter and the non-shooter were in the same range.This study highlights that the secondary transfer must be taken into account in the interpretation of OGSR. Indeed, an individual's hands might be contaminated by handling a firearm or having physical contact with a shooter.     

Comparison of GSR Composition Occurring at Different Locations Around the Firing Position

Abstract: Variations in gunshot residue (GSR) compositions are used in the reconstruction of shooting incidents. In this study, GSR samples taken from seven different locations around and in the firearm were collected and analyzed using scanning electron microscopy/energy dispersive X‐ray analysis. Four different types of ammunition were applied. Very low correlations were found when different ammunition were used. This clearly shows that it is possible to differentiate between ammunition types. When the same ammunition was used, high correlations were found between samples taken from external positions (such as hands of shooter, bullet‐entrance holes) but poor correlation was found between internal samples (such as firearm barrel, cartridge case) and external samples. A high degree of association was found between samples that simulated victim and shooter. These findings clearly demonstrate that GSR comparison studies are meaningful but care needs to be taken when choosing suitable exhibits. External samples (such as hands of shooter, bullet‐entrance holes) are more suitable candidates than internal samples (barrel of the firearm, cartridge case).     

Identification of firearms holders by the [Fe(PDT)3](+2) complex. Quantitative determination of iron transfer to the hand and its dependence on palmar moisture levels

Quantitative data are reported for the first time on the amounts of iron, which are transferred to the hand upon holding a firearm. Iron levels between 21-315 ng/cm2 were found on volunteers' palms after a single holding of a handgun. Determination of the iron traces was accomplished spectrophotometrically using 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT) as a complexing agent. The transfer of iron from firearms to the palm was found to be, by and large a chemical (dissolution) rather than mechanical dislodgement. The prime factor that determines the amount of iron transferred from the firearm to the hand is the moisture level on the palm. These findings are likely to be of importance in courts of law, as well as in the war against terrorism and serious crime.     

Fatal firearm accidents in Sweden

According to Swedish law, it is prohibited to possess and use firearms without a special permission (license), which is given only after a detailed personal investigation. This restrictive legislation accounts for the fact that deaths due to firearms in Sweden are rare in an international comparison. The number of accidental firearm fatalities in Sweden is 0.074/100,000 living persons. We have previously published a series of accidental firearm fatalities during hunting, and now we present an investigation on the non-hunting fatalities. The mean age of the victims was 27 years, and males predominated. Handguns, military rifles, and shotguns caused most of the accidents. The first published case of fatal thoracic airgun wound is also included. Slightly more than half of the accidents were caused by another person and were inflicted at close range. Unsafe handling of the guns, especially "playing" with the gun or during military training caused most of the accidents. It is doubtful that one could further decrease the low number of fatal firearm accidents in Sweden by even more restrictive legislation. Instead, it is concluded that the most important factor to stress is the safer handling of weapons.     

Form follows function: Applying photographic content analysis to forensic firearm identification

Drawing forensic conclusions from an image or a video is known as “photographic content analysis.” It involves the analysis of an image, as well as objects, actions, and events depicted in images or video. In recent years, photographic depictions of objects suspected as illegal firearms have substantially increased, appearing on CCTV surveillance footage, captured by mobile phones and shared on social media. However, the law in Israel states that a person can be charged with illegally possessing a firearm only if it can be proven that the object is capable of shooting with lethal bullet energy. This becomes more challenging in cases where the firearm was not physically seized, and the evidence exclusively consists of images and video. In this study, photographic content analysis was applied to images and video where objects suspected as commercial or improvised firearms had been depicted. An image and event sequence reconstruction video databases of both firearms and replicas were created in order to better define firearm-specific functional morphological features. We demonstrate that it is possible to classify an object as a firearm by analyzing the functional, and not only the esthetic, morphology in images and video. It is also shown that event sequence reconstruction in video may be used to infer that an object suspected as a firearm has the capacity to shoot by confirming the occurrence of a shooting act or shooting process. Thus, photographic content analysis may be used to forensically establish that an object depicted in an image or a video is a firearm by ruling out other known scenarios, and without physically seizing it.     

Distribution of GSR particles in the surroundings of shooting pistol

Several series of experiments were performed to study the distribution of GSR particles in seven directions in the surroundings of shooting firearm (pistol CZ 85 caliber 9 mm Luger). External and internal conditions and two different primer types were used for the shooting experiments. The results showed that maximum number of GSR particles could be found in the right front quadrant at a distance of 2–4 m with respect to the shooting firearm position and shooting direction. GSR particles were even found in distance 10 m from shooting firearm. A significant influence of climatic conditions on GSR distribution was confirmed.     

Evaluation of match criteria used for the comparison of refractive index of glass fragments

For comparative glass examinations, the refractive indices (RIs) of recovered glass fragments are often compared to a test interval defined by measurements from a broken glass object. RI measurements from five modern float glasses were used via resampling to assess the frequencies of false exclusion errors for eight test criteria as functions of the number of measurements. The test criteria were based on ranges, fixed intervals, and multiples of standard deviations of the known source measurements. The observed error rates for the eight tests studied are between zero and c. 35%, depending upon the match criteria, the number of measurements, and the RI distribution for a glass source. The results of this study can be used to predict the false exclusion rate for a test criterion under a given set of conditions or to select test criteria that result in a desired error rate for these typical sheet glasses.     

Automatic rifle injuries: suicide by eight bullets. Report of an unusual case and a literature review

A 25-year-old man committed suicide by shooting himself with eight bullets fired from a military rifle set on automatic. This rifle has two firing modes: an automatic mode and a self-loading, single-shot mode. Using this case as an example, some important aspects of firearm injuries are discussed with special emphasis on those points that are relevant to automatic military rifles and most applicable to forensic pathology practice. Some of the pathologic features of firearm wounds are reviewed and the role of the pathologist is discussed. Lastly, the most important points that help the pathologist to determine the type or nature of a firearm death--that is, whether it is an accident, homicide, or a suicide--are discussed. Classically, the number of the firearm wounds is used to differentiate suicide from homicide. As in the case reported here, however, when an automatic rifle or a military rifle set on automatic is used, the number of wounds is not a reliable indicator of the type of death.     

The consequences of potentially differing distributions of the refractive indices of glass fragments from control and recovered sources

In forensic cases involving glass evidence, the variance of the recovered glass refractive index (RI) has been observed to be larger than the variance of the control glass RI. This has consequences for subsequent interpretation. To investigate this phenomenon, a study was made of the probable distributions of refractive indices of the recovered glass given a range of casework type scenarios involving breakage and backscatter. An investigation of the consequences of any distribution differences with regard to casework was also made. It was discovered that the inclusion of surface fragments from the float surface of the glass can have a profound effect on the comparison of recovered and control glass samples. The effect was largest when a breaker was striking the float surface of a window. In particular, it was found that the inclusion of a few surface fragments even post grouping is sufficient by itself to explain the observed differences in variance of RI between control and recovered groups. Surface fragments, if present, are very likely to be treated as outliers and to be deemed as non-matching. The findings of this paper challenge routine glass examination procedure and suggest that knowledge of which surface is facing the striker is valuable information in interpretation.     

Deterrence,Firearm Arrests,and Subsequent Shootings: A Micro-Level Spatio-Temporal Analysis

Do police firearm arrests reduce later shootings in nearby locations and in the days immediately following the arrest? This question is examined at a more detailed level than in previous work in order to better describe the spatio-temporal dynamics linking these two event types. All firearm arrests (n?=?5,687) and shootings (n?=?5,870) in Philadelphia from 2004 to 2007 were analyzed using a modified close-pair method. Following a firearm arrest shootings declined significantly, 28–47% up to a couple of blocks away. These significant declines, however, lasted for just a few days. Overall, results suggest police firearm suppression effects occur, may extend up to two blocks away from a firearm arrest, but also are short-lived. Potential implications for deterrence are discussed.     

A parameter study regarding the IBIS correlator

The electronic system IBIS has been used by numerous agencies worldwide as the standard tool to compare firearm markings on bullets and fired cartridges. There is a general interest among users concerning the likelihood with which the IBIS correlator may locate hits in its databases. Test results of the performance under different test conditions have been published in various papers. Experience has also been gained with the IBIS system from years of practical usage. All of these findings are difficult to compare with each other. No systematic presentation exists that actually shows the parameters upon which the success rate of the IBIS correlator depends. There has also been no mention of what values these parameters take on during each test. This paper first generally defines the success and error rates of the IBIS correlator. The parameters used will be discussed. Results of previously published tests will be re-examined based on this methodology. An illustrative form of presentation for the success rate of an electronic comparison system will also be suggested. It will be shown that the success rate of the IBIS correlator highly depends on the quality of the firearms-generated markings. It increases with the number of considered mark types, the number of available signatures per firearm, and the number of items inspected in the hit list. The success rate decreases with the database size. The paper will conclude with a series of practical recommendations for the setting up and successful operation of an electronic collection of ballistic evidence.     

An investigation of bulk and surface refractive indices for flat window glasses,patterned window glasses and windscreen glasses

The bulk and surface refractive indices have been measured for 20 float window glasses, 20 non-float window glasses, 20 patterned window glasses and 20 toughened float windscreen glasses.The refractive index of the tin-contact surface of the float glasses was always greater than that of the bulk, typically by 0.002 (range 0.00053–0.00307). In contrast the refractive indices of the two surfaces and the bulk of the sheet window glasses were in agreement within accepted experimental error in each case. A number of patterned window glasses showed significantly different refractive indices between the plain and patterned surfaces, the largest difference obtained (0.00021) being an order of magnitude smaller than that found for a typical float glass.Nine of the 40 float glasses examined yielded abnormal fragments from the upper surface in the sense that they did not disappear at the match temperature of the bulk glass. The refractive index measured from these abnormal fragments for two of these glasses was lower than the refractive index from the bulk glass.The variation in the bulk refractive index for the sheet and float window glasses produced an estimated standard deviation (E.S.D.) of 1.2 × 10^?5. However, the patterned glasses were nearly three times as variable (E.S.D. = 3.3 × 10^?5) and the toughened float glasses were, on average, almost seven times as variable (E.S.D. = 8.0 × 10^?5).The value of making surface as well as bulk refractive index measurements in routine casework is discussed in the light of the above results.     

Fate and Behavior of Gunshot Residue—A Review

A review of the literature concerning the fate and behavior of gunshot residue (GSR) is presented. A number of concomitant parameters including firearm and ammunition type, plume and GSR material characteristics, travel distances, chemical composition and GSR morphology are critically discussed in relation to their effects on the distribution and deposition, transfer and persistence processes of GSR. The underlying mechanisms associated with such processes are also considered. Knowledge of these processes on GSR materials could provide valuable information concerning scene preservation and subsequent forensic sampling. The number of GSR particles deposited can vary significantly with each firearm discharge, highlighting the potential to produce distinctive data in each individual case. With the continual development and compositional changes of new ammunition types, further evaluation of the effect these processes may have on GSR evidence and their possible influence on the interpretation of the analytical results should be given due consideration.     

The impact of TASERs on police use-of-force decisions: Findings from a randomized field-training experiment

This paper presents findings from a randomized field-training experiment designed to study the impact TASERs on police officers’ use-of-force decisions. Officers were randomly assigned to either a treatment group (with TASERs) or a control group (without TASERs) and then participated in training scenarios involving different levels of suspect resistance. The study investigates whether and to what extent officers armed with the TASER use it as an alternative to other types of less-lethal force (e.g., empty hands, pepper spray, and the baton) and the firearm, controlling for the level of suspect resistance. The findings indicate that officers who were armed with the TASER were significantly less likely to deploy pepper spray and the baton in response to aggressive physical resistance. Additionally, the results show that officers equipped with the TASER were less likely to discharge their firearm when confronted with suspect resistance that was potentially lethal. No differences in police behavior occurred in response to passive suspect resistance.     

Comparison of gunshot wounds and field-tipped arrow wounds using morphological criteria and chemical spot tests

Arrow wounds represent an unusual class of wounds rarely seen by most death investigators. Although the edged, broadhead-tipped arrow produces a wound usually characteristic of archery/crossbow weapons, the plain, field-tipped arrow wound can be confused with gunshot injuries in those cases in which powder residue or firearm projectiles or fragments or both are not recovered. We present a case of a deer carcass with a wound of uncertain firearm or archery origin which initiated a comparison of firearm wounds and archery wounds on fresh road-killed deer. We found the following features to be valuable in the differentiation of gunshot wounds and field-tipped archery wounds: First, the majority of the gunshot wounds (but none of the arrow wounds) had identifiable, macroscopic, wipe-off material and chemically identifiable wipe-off residue by spot test. Second, the archery wound defects had very inconspicuous abrasion rings as compared to the often prominent abrasion rings of gunshot wounds. Third, the actual central defect in the archery wounds was more likely to be oblong or slit-like compared to the gunshot wound defects, which were more likely to be round.     

Domestic Homicide: Neuropsychological Profiles of Murderers Who Kill Family Members and Intimate Partners

Domestic homicide is the most extreme form of domestic violence and one of the most common types of homicide. The objective was to examine differences between spontaneous domestic homicide and nondomestic homicide offenders regarding demographics, psychiatric history, crime characteristics, and neuropsychological status, utilizing neuropsychological test data from forensic examinations of 153 murderers. Using standard crime classification criteria, 33% committed spontaneous domestic homicides (SDH) and 61% committed nondomestic homicides (NDH). SDH offenders were more likely to manifest psychotic disorders, but less likely to be diagnosed with antisocial personality disorder or to have prior felony convictions. SDH offenders manifested significantly worse neuropsychological impairments than NDH offenders. The mean number of victims was lower for the SDH than the NDH group and only 14% of SDH offenders used a firearm, whereas 59% of NDH offenders used a firearm. These findings corroborate the notion that spontaneous domestic homicide may represent a discernible criminological phenotype.     

The classification and discrimination of glass fragments using non destructive energy dispersive X-ray microfluorescence

Frequency of analytical characteristics is best estimated on glass recovered at random. However, as such data were not available to us, we decided to use control windows for this estimation. In order to use such a database, one has to establish that the recovered fragment comes from a window. Therefore, elemental analysis was used both for classification and discrimination of glass fragments. Several articles have been published on the subject, but most methods alter the glass sample. The use of non destructive energy dispersive X-ray microfluorescence (microXRF) for the analysis of small glass fragments has been evaluated in this context. The refractive index (RI) has also been measured in order to evaluate the complementarity of techniques. Classification of fragments has been achieved using Fisher's linear discriminant analysis (LDA) and neural networks (NN). Discrimination was based on Hotelling's T2 test. Only pairs that were not differentiated by RI followed by the Welch test were studied. The results show that neural network and linear discriminant analysis using qualitative and semi-quantitative data establishes a classification of glass specimens with a high degree of reliability. For discrimination, 119 windows collected from crime scene were compared: using RI it was possible to distinguish 6892 pairs. Out of 129 remaining pairs, 112 were distinguished by microXRF.     

Development of STR profiles from firearms and fired cartridge cases

Fired cartridge cases are a common type of evidence found at crime scenes. However, due to the high chamber temperatures and touch nature of this evidence, DNA testing is not commonly sought because it is believed DNA is only present in low levels, whether it is due to initial low levels of DNA and/or DNA degradation from the heat or inhibition of the PCR reaction. Moreover, very few laboratories report STR typing success with fired cases. This study focused on obtaining STR profiles from fired cartridge cases using the AmpFℓSTR^® MiniFiler™ kit, which is designed to amplify DNA from low level, inhibited, and degraded samples. Comparisons to other STR amplification kits were also conducted. In attempt to simulate casework, random individuals loaded cartridges into a firearm. DNA was recovered from the fired cartridge cases using the double swab technique and extracted using an automated large volume DNA IQ™ method. Initially, testing focused on known shedders handling cartridges for 30 s prior to firing. A significantly greater number of alleles was obtained following amplification with the MiniFiler™ kit versus the PowerPlex^® 16 BIO kit. No alleles were observed using the Identifiler^® kit. In an attempt to better simulate casework, a random selection of laboratory personnel handled shotshells for as long as needed to load and fire the weapon. In this mock sample study, the MiniFiler™ kit successfully amplified an average of 22% of expected alleles from DNA recovered from shotshell cases versus the PowerPlex^® 16 BIO kit where an average of 7% of alleles were observed. However, the total number of alleles obtained from the two kits was not significantly different. The quality of the DNA obtained from fired cases was studied with evidence of inhibition in at least 11% of shotshell case samples. After swabbing the head and the hull of three shotshell cases separately, a significantly greater number of alleles was obtained from the hull as opposed to the head of the fired shotshell case. In addition, after firing, various internal firearm surfaces were swabbed, including the chamber of barrel, ejection port, and breechface, in an attempt to obtain amplifiable DNA. DNA was obtained from the chamber of the barrel and was amplifiable using the MiniFiler™ kit, although mixtures were obtained with extensive drop-in and drop-out making this analysis unlikely to aid an investigation.     

An Investigation into Whether or Not the Class and Individual Characteristics of Five Turkish Manufactured Pistols Change During Extensive Firing

Abstract:  In order to assess whether or not the class and individual characteristics of a firearm change over time, five different makes of Turkish self-loading pistol were tested and were each fired a large number of times. The class and individual characteristics were identified for each pistol and the first fired cartridge case was compared with the subsequent consecutive 250th fired cases for each pistol. It was found that there were slight changes in some of the individual and class characteristics; however, this was not statistically significant and did not affect the ability of the firearms examiner to match the first fired case to the last fired case for each firearm tested.     

Comparison of glass fragments using particle-induced X-ray emission (PIXE) spectrometry

A procedure has been developed to analyze the trace element concentrations in glass fragments using particle-induced X-ray emission (PIXE) spectrometry. This method involves using accelerated protons to excite inner-shell electronic transitions of target atoms and recording the resultant X-rays to characterize the trace element concentrations. The protocol was able to identify those glass fragments that originated from different sources based on their elemental analyses. The protocol includes specific approaches to calculating uncertainties and handling measurements below the level of detection. The results indicate that this approach has increased sensitivity for several elements with higher atomic number compared with X-ray fluorescence methods. While not as sensitive as laser-ablation or inductively coupled plasma mass spectrometry methods of dissolved samples, it is entirely nondestructive and entails a much simpler sample preparation process that may be used to presort glass fragments for more comprehensive elemental analysis. As such, the technique described may have a niche role in forensic glass analysis.