Dynamic pressure measurement of cartridge operated vole captive bolt devices

IntroductionVole captive bolt devices are powder actuated spring guns that are used as a pest control mean. After having triggered the explosion of the blank cartridge by touching a metal ring around the muzzle, the vole is killed by the massive propulsion of the gas jet. Improper use and recklessness while handling these devices may cause severe injuries with the hand of the operator at particular risk. Currently, there are no experimental investigations on the ballistic background of these devices.MethodsAn experimental test set-up was designed for measurement of the firing pressure and the dynamic force of the gas jet of a vole captive bolt device. Therefore, a vole captive bolt device was prepared with a pressure take-off channel and a piezoelectric transducer for measurement of the firing pressure. For measurement of the dynamic impact force of the gas jet an annular quartz force sensor was installed on a test bench. Each three simultaneous measurements of the cartridges’ firing pressure and the dynamic force of the blast wave were taken at various distances between muzzle and load washer.ResultsThe maximum gas pressure in the explosion chamber was up to 1100 bar. The shot development over time showed a typical gas pressure curve. Flow velocity of the gas jet was up to 2000 m/s. The maximum impact force of the gas jet at the target showed a strong inverse ratio to the muzzle's distance and was up to 11,500 N for the contact shot distance. Energy density of the gas jet for the close contact shot was far beyond the energy density required for skin penetration.ConclusionThe unique design features (short tube between cartridge mouth and muzzle and narrow diameter of the muzzle) of these gadgets are responsible for the high firing pressure, velocity and force of the gas jet. These findings explain the trauma mechanics of the extensive tissue damage observed in accidental shots of these devices.     

Noise Trauma Induced by a Mousetrap—Sound Pressure Level Measurement of Vole Captive Bolt Devices

Abstract: While ballistic parameters of vole captive bolt devices have been reported, there is no investigation on their hazardous potential to cause noise trauma. The aim of this experimental study was to measure the sound pressure levels of vole captive bolt devices. Two different shooting devices were examined with a modular precision sound level meter on an outdoor firing range. Measurements were taken in a semi‐circular configuration with measuring points 0° in front of the muzzle, 90° at right angle of the muzzle, and 180° behind the shooting device. Distances between muzzle and microphone were 0.5, 1, 2, 10, and 20 m. Sound pressure levels exceeded 130 dB(C) at any measuring point within the 20‐m area. Highest measurements (more than 172 dB[C]) were taken in the 0° direction at the 0.5‐m distance for both shooting devices proving the hazardous potential of these gadgets to cause noise trauma.     

A novel hunting accident. Discharge of a firearm by a hunting dog

The authors report the case of a 21-year-old man who was killed while duck hunting when a shotgun accidentally discharged, shooting him in the head. The loaded weapon, which had been lying on the ground with the safety off and the muzzle pointed toward a river a few feet away, discharged when a hunting dog stepped on the trigger. Scene investigation confirmed that the victim had been standing in the river, planting decoys, with his head approximately level with the adjacent bank. Autopsy examination and ballistic testing confirmed a range of fire consistent with the witness' statements. Examination of the weapon in question documented a light trigger pull but no mechanical defects. The authors review the epidemiology and causality of hunting accidents and discuss the various safety rules that were violated in this highly unusual case. The importance of a complete death investigation, including autopsy, when dealing with a firearm death is emphasized.     

Utilization of X‐ray Computed Tomography for the Exclusion of a Specific Caliber and Bullet Type in a Living Shooting Victim

A bystander claimed to have been shot by a police officer, and CT scans were used to match qualitative and quantitative aspects of the unremoved bullet with police issued 9 mm Luger ammunition. CT scan methodology proved a valid approach for the measurement of bullets based on calculated measurement capability and correlation with “gold standard” physical measurement by vernier caliper. Measurements regarding length and base diameter, as well as length/diameter ratio, were insufficient to unambiguously identify a specific caliber, or a bullet of specific mass within a caliber class. It was, however, possible to exclude a bullet of specific design and mass with well‐characterized precision and accuracy values under selected CT scan conditions. A 9 mm Luger bullet (115 gr FMJ RN) was excluded from involvement in a shooting based on qualitative bullet shape combined with length, base, and ratio measurements of the bullet in‐situ for the victim.     

Estimating Biological Characteristics With Virtual Laser Data

Laser scanning technology is increasingly being used in forensic anthropological research to obtain virtual data for archival purposes and post hoc measurement collection. This research compared the measurement accuracy of two laser scanners—the FARO Focus^3D 330X and the FARO Freestyle^3D—against traditionally obtained (i.e., by hand) control data (N = 454). Skeletal data were collected to address a novel question: the ability of laser scanning technology to produce measurements useful for biological characteristic estimation, such as sex and stature. Results indicate that both devices produced measurements very similar to control (c. 3‐mm average absolute error), but also illuminate a tendency to under‐measure. Despite these findings, the virtual data produced sex and stature estimates that varied little from control‐produced estimates, signifying the usefulness of virtual data for preliminary biological identification when the skeletal elements are no longer available for physical analysis.     

Accuracy of facial soft tissue thickness measurements in personal computer-based multiplanar reconstructed computed tomographic images

The purpose of this study was to determine the precision and accuracy of facial soft tissue measurement using personal computer (PC)-based multiplanar reconstructed (MPR) computed tomography (CT) images and to evaluate the effect of the various CT scanning protocols on the facial soft tissue thickness measurement. Thirteen different CT imaging protocols were used to image a cadaver head. MPR reformations and three-dimensional (3D) reconstructions viewed on a laptop PC were used to make measurements at six specific sites on each set of images. These measurements were compared to physical measurements at the same sites. Increasing the slice thickness resulted in decreased image quality. Within the same slice thickness, increasing the pitch ratio in the spiral mode, resulted in decreasing image quality. The image quality of conventional CT scanning was relatively poorer than that of the spiral CT scanning. However, the mean deviation from the physical measurement was within 0.43 mm in every instance. This mean deviation was quite small and clinically acceptable for measuring the soft tissue thickness of the facial area. PC-based MPR CT images of the face using routine scanning CT protocols can be used to accurately measure soft tissue thickness in the facial region. However, for more fine and accurate data collection, scanning protocols with slice thicknesses less than 5mm, and a spiral/helical mode pitch less than 2:1 are recommended.     

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.     

In vitro accuracy and precision studies comparing direct and delayed analysis of the ethanol content of vapor

In vitro accuracy and precision studies were conducted using silica gel, magnesium perchlorate, and indium encapsulation breath collection tubes in conjunction with three infrared breath ethanol analyzers (BAC Verifier, Intoxilyzer 5000, and Intoximeter 3000), the Breathalyzer 900A, and the GC Mark IV. Statistical analyses revealed good accuracy and precision and correlation between direct and delayed vapor ethanol analyses for each combination of instruments and collection devices (range = 0.000 to 0.250 g/210 L, N = 42/instrument, r greater than 0.99). Delayed vapor ethanol analysis utilizing each instrument and collection device combination appears to predict satisfactorily original vapor ethanol concentrations.     

The Accuracy and Repeatability of Reconstructing Single Bullet Impacts Using the 2D Ellipse Method

When a bullet punctures a surface, it leaves behind a bullet impact, which can be analyzed in order to determine the origin and trajectory path from which a bullet was discharged using many different scientific methods to reconstruct a shooting scene. The purpose of the research was to test the accuracy and repeatability of reconstructing the impact angle of single bullet impacts using the ellipse method. The research was conducted by firing various calibers of ammunition into drywall panels positioned at varying angles of incidence from 88° until ricochet occurred. This was done in order to determine which caliber type and angle of incidence are most accurate and precise for reconstructing a shooting scene. The study examined four caliber types fired into drywall panels, with 5 repeated shots for each of the 11 angles of incidence (n = 220). Furthermore, 31 participants partook in the study to estimate a bullet impact angle of incidence utilizing the ellipse method. The results show that the best performance (accuracy and repeatability) is seen with the measurements of the 0.45 caliber ammunition. When angle of incidences is low (<64°), the performance (accuracy and repeatability) was seen to be better in all caliber ammunitions. Overall, the data provided for single bullet impacts deposited in drywall show that the ellipse method is useful in providing measurements for most crime scene reconstruction purposes and has also demonstrated that results vary depending on the type of ammunition, firearm, and angle of incidence being examined.     

Estimation of stature from hand and handprint dimensions in a Western Australian population

As part of the formulation of a biological profile, the estimation of stature is an important element that provides useful data towards narrowing the pool of potentially matching identities. Recent literature has demonstrated that anthropometry of the hand has considerable promise for the accurate estimation of stature; although the technique has only been tested in a relatively limited range of populations. The aim of the present study, therefore, is to assess the reliability and accuracy of using anthropometric hand measurements for the estimation of stature in a contemporary Western Australian population; we also evaluate whether stature can be accurately estimated from the measurement of handprints. The study sample comprises 91 male and 110 female adult individuals. Following the measurement of stature, seven measurements are taken on each hand and its corresponding print. To establish the reliability of acquiring these measurements, a precision study was performed prior to primary data collection. Measurements data are analysed using basic univariate statistics and simple and multiple regression analyses. Our results show that the degree of measurement error and reliability are well within accepted standards. Stature prediction accuracy using hand and handprint measurements ranges from ±4.74 to 6.53cm, which is comparable to established skeletal standards for the hand. This study provides new forensic standards for the estimation of stature in a Western Australian population and also demonstrates that the measurement and analysis of handprints affords a novel source of profiling data that is statistically quantified.     

Tooth hop variability in human and nonhuman bone: Effect on the estimation of saw blade TPI

Forensic research has demonstrated that tooth hop (TH) is a valuable measurement from saw-cut bones as it can be used to estimate teeth-per-inch (TPI) of a saw used in postmortem dismemberment cases. However, error rates for TPI estimation are still under development and knowledge of how bone tissue affects TH measurements remains unclear. The purpose of this research was to investigate the effects of tissue variability through the use of different taxa on the accuracy and precision of TH measurements in the bone to estimate TPI of the blade. A total of 1766 TH measurements were analyzed from human, pig, and deer long bones cut by two 7 TPI saw blades of different tooth type. Fifty distance-between-teeth measurements before and after sawing were collected directly from each blade for comparison to bone-measured TH to assess potential effects of tooth wear on TH variability. ANOVA and F tests were used to compare mean TH and variance, respectively, by saw-species (i.e., crosscut-deer, rip-deer) and species groups (i.e., all deer, all pig), with significance determined at the p < 0.05 level. TH measurements were converted to usable TPI ranges, which would typically be presented in a forensic report. It is concluded that significant differences in TH (mm) do not necessarily reflect significant differences in associated TPI ranges of suspect blades. Forensic reports should report mean TPI ± 1.5–2.5 TPI while providing a sample size indicating number of TH measured rather than just number of cuts or cut surfaces examined.     

Testing a Novel 3D Printed Radiographic Imaging Device for Use in Forensic Odontology

There are specific challenges related to forensic dental radiology and difficulties in aligning X‐ray equipment to teeth of interest. Researchers used 3D printing to create a new device, the combined holding and aiming device (CHAD), to address the positioning limitations of current dental X‐ray devices. Participants (N = 24) used the CHAD, soft dental wax, and a modified external aiming device (MEAD) to determine device preference, radiographer's efficiency, and technique errors. Each participant exposed six X‐rays per device for a total of 432 X‐rays scored. A significant difference was found at the 0.05 level between the three devices (p = 0.0015), with the MEAD having the least amount of total errors and soft dental wax taking the least amount of time. Total errors were highest when participants used soft dental wax—both the MEAD and the CHAD performed best overall. Further research in forensic dental radiology and use of holding devices is needed.     

Suicide by Cop Among Officer-Involved Shooting Cases

Abstract: The frequency and characteristics of suicide by cop cases (SBC) among a large (n = 707) nonrandom sample of North American officer-involved shootings (OIS) were investigated. “Suicide by cop” is when a subject engages in behavior which poses an apparent risk of serious injury or death, with the intent to precipitate the use of deadly force by law enforcement against the subject. Thirty-six percent of the OIS in this sample were found to be SBC with high interrater agreement (intraclass correlation coefficient = 0.93) for category classification. SBC cases were more likely to result in the death or injury of the subjects than regular OIS cases. Most SBC cases were spontaneous, but had clear verbal and behavioral indicators that occurred prior to, and during the event. Findings confirm the trend detected in earlier research that there was a growing incidence of SBC among OIS. SBC individuals had a high likelihood of possessing a weapon (80%), which was a firearm 60% of the time. Half of those with a firearm discharged it at the police during the encounter. Nineteen percent simulated weapon possession to accomplish their suicidal intent. Other findings highlight the histories and commonalities in this high risk group.     

Hierarchical,Three‐Dimensional Measurement System for Crime Scene Scanning

We present a new generation of three‐dimensional (3D) measuring systems, developed for the process of crime scene documentation. This measuring system facilitates the preparation of more insightful, complete, and objective documentation for crime scenes. Our system reflects the actual requirements for hierarchical documentation, and it consists of three independent 3D scanners: a laser scanner for overall measurements, a situational structured light scanner for more minute measurements, and a detailed structured light scanner for the most detailed parts of tscene. Each scanner has its own spatial resolution, of 2.0, 0.3, and 0.05 mm, respectively. The results of interviews we have conducted with technicians indicate that our developed 3D measuring system has significant potential to become a useful tool for forensic technicians. To ensure the maximum compatibility of our measuring system with the standards that regulate the documentation process, we have also performed a metrological validation and designated the maximum permissible length measurement error E_MPE for each structured light scanner. In this study, we present additional results regarding documentation processes conducted during crime scene inspections and a training session.     

The COLLECTORS ranking scale for ‘at‐scene’ digital device triage

As digital evidence now features prominently in many criminal investigations, such large volumes of requests for the forensic examination of devices has led to well publicized backlogs and delays. In an effort to cope, triage policies are frequently implemented in order to reduce the number of digital devices which are seized unnecessarily. Often first responders are tasked with performing triage at scene in order to decide whether any identified devices should be seized and submitted for forensic examination. In some cases, this is done with the assistance of software which allows device content to be “previewed”; however, in some cases, a first responder will triage devices using their judgment and experience alone, absent of knowledge of the devices content, referred to as “decision‐based device triage” (DBDT). This work provides a discussion of the challenges first responders face when carrying out DBDT at scene. In response, the COLLECTORS ranking scale is proposed to help first responders carry out DBDT and to formalize this process in an effort to support quality control of this practice. The COLLECTORS ranking scale consists of 10 categories which first responders should rank a given device against. Each devices cumulative score should be queried against the defined “seizure thresholds” which offer support to first responders in assessing when to seize a device. To offer clarify, an example use‐case involving the COLLECTORS ranking scale is included, highlighting its application when faced with multiple digital devices at scene.     

The systemic error in the vertical component of handgun bullet trajectory reconstructions

Establishing the path or trajectory of a fired bullet is an often recurring part of shooting incident reconstruction. The current study describes how gravitational pull causes a systemic error on the vertical component of a trajectory reconstruction. Bullet drop, drop angle, and vertical offset are explained and calculated for 10 different handgun/ammunition combinations over a range of distances up to 100 m. The presented results are intended to provide forensic firearm examiners with a reference frame for the magnitude of error introduced on handgun bullet trajectory reconstructions over distance. Threshold values of 20 and 30 m are proposed as conservative distances up to where bullet trajectories can be modeled as straight lines with subsonic/transonic handgun bullets and with supersonic handgun bullets respectively. Both the bullet drop and vertical offset will be below 5 cm at these distances for those categories. The drop angle will be below 0.3°.     

A Validation Study of Bullet and Cartridge Case Comparisons Using Samples Representative of Actual Casework

The foundation of firearm and tool mark identification is that no two tools should produce the same microscopic marks on two separate objects that they would be inaccurately or wrongly identified. Studies addressing the validity of identification infrequently employ tests that mirror realistic casework scenarios. This study attempted to do so using a double‐blind process, reducing test‐taking bias. Test kits including bullets and cartridge cases but not the associated firearms were completed by 31 analysts from 22 agencies. Analysis of the results demonstrated an overall error rate of 0.303%, sensitivity of 85.2%, and specificity of 86.8%. Variability in performance across examiners is addressed, and the effect of examiners’ years of experience on identification accuracy is explored. Finally, the article discusses the importance of studies using realistic case work scenarios when validating the field's performance and in providing courts with usable indicators of the accuracy of firearm and tool mark identification.     

Firearm Ownership in High-Conflict Families: Differences According to State Laws Restricting Firearms to Misdemeanor Crimes of Domestic Violence Offenders

This study examines the association between state laws that prohibit firearm ownership for offenders convicted of misdemeanor crimes of domestic violence (MCDV) and firearm ownership in two-parent families with high-conflict male partners with arrest histories. Mixed effects logistic regression models applied to data from the Early Childhood Longitudinal Study-Birth cohort (n?= 5350) determined that living in a state with laws that prohibited firearm ownership for convicted MCDV offenders decreased the likelihood of firearm ownership among families with high-conflict males by 62%. The length of the time limit on firearm prohibition was correlated with incremental decreases in firearm ownership in such families, with the probability of firearm ownership among families with high-conflict males decreasing from 30% in states with no MCDV laws restricting access from firearms to 12% in states with permanent prohibition on firearm ownership. These findings have significance for public health policy aimed at decreasing intimate-partner homicide.