Gunshot Residue Deposition Research Articles

Gunshot Residue Deposition With and Without Firearm Suppressors (Silencers).

Forensic pathologists recognize the importance of estimating the range of fire for gunshot entrance wounds. Classically described ranges of fire include contact, close range, medium (or intermediate) range, and indeterminate (or distant) range. The presence or absence of gunshot residue (smoke/soot and/or gunpowder) and the characteristics of the gunshot residue are evaluated in order to estimate the range of fire. It is well known that interposed targets can block or otherwise alter gunshot residue deposition. In this preliminary study, a comparison is made between gunshot defects produced on targets using firearms with and without an attached suppressor device (so-called "silencer"). Comparisons are made at various distances from the targets, using multiple weapon/ammunition calibers.

Forensic volumetric visualization of gunshot residue in its anatomic context in forensic post mortem computed tomography: Development of transfer function preset

• Technical development of a fast implementation for use of preset function. • Relevant visualization for Gunshot Residue in Forensic Routine PMCT. • Statistical basis for preset function based on probabilistic model. While the visualization of gunshot injuries so far focused on solid metal density in routine forensic post mortem computed tomography (PMCT) as well as in micro-computed tomography, gunshot residue (GSR) as dispersed metal particles typically succumbs to partial volume effect. A case series of seven contact shots to the head was evaluated to determine a density range for GSR with at least three times higher likelihood than encountering bone, skin, muscle or blood. For that, a Bayesian likelihood was determined from normal distributions of the CT-densities of blood, bone, skin, muscle and GSR as identified in correlation with visual evidence. Resulting transfer functions matched ring and cone shaped GSR deposits as published elsewhere, thus representing a plausible result. Only fast and plausibly specific visualization is suitable for routine use in forensic PMCT, to allow the examination of GSR in real cases on a wider scale.

Transfer and Distribution of Gunshot Residue through Glass Windows.

Research into the deposition patterns of primer gunshot residue (GSR) beyond a primary target was previously nonexistent. This study aimed to determine the deposition patterns of GSR once a bullet passed through an initial target and continued on its path into additional targets. Multiple repetitions were performed to assess the GSR deposition patterns after a bullet was shot through a closed window into either a dummy or a wall within an enclosed room. Samples were taken from both the primary and secondary target holes as well as from nontarget areas. Significant amounts of GSR were found on all samples. The results show that GSR continues to be deposited along the path of the bullet after passing through a primary glass target. These findings reiterate the lack of probative value in collecting GSR samples from gunshot victims even if they are in an enclosed area separate from the shooter.

Micro-CT features of intermediate gunshot wounds severely damaged by fire

Incineration or extensive burning of the body, causing changes in the content and distribution of fluids, fixation and shrinking processes of tissues, can alter the typical macroscopic and microscopic characteristics of firearm wounds, hampering or at least complicating the reconstruction of gunshot fatalities. The present study aims at evaluating the potential role of micro-computed tomography (micro-CT) for detecting and quantifying gunshot residue (GSR) particles in experimentally produced intermediate-range gunshot wounds severely damaged by fire. Eighteen experimental shootings were performed on 18 sections of human calves surgically amputated for medical reasons at three different firing distances (5, 15 and 30cm). Six stab wounds produced with an ice pick were used as controls. Each calf section underwent a charring cycle, being placed in a wood-burning stove for 4min at a temperature of 400°C. At visual inspection, the charred entrance wounds could not be differentiated from the exit lesions and the stab wounds. On the contrary, micro-CT analysis showed the presence of GSR particles in all burnt entrance gunshot wounds, while GSR was absent in the exit and stab wounds. The GSR deposits of the firearm lesions inflicted at very close distance (5cm) were mainly constituted of huge particles (diameter >150μm) with an irregular shape and well-delineated edges; at greater distances (15 and 30cm), agglomerates of tiny radiopaque particles scattered in the epidermis and dermis layers were evident. Statistical analysis demonstrated that also in charred firearm wounds the amount of GSR roughly correlates with the distance from which the gun was fired. The obtained results suggest that micro-CT analysis can be a valid screening tool for identifying entrance gunshot wounds and for differentiating firearm wounds from sharp-force injuries in bodies severely damaged by fire.

Passive Exposure and Persistence of Gunshot Residue (GSR) on Bystanders to a Shooting: Comparison of Shooter and Bystander Exposure to GSR

Gunshot residue (GSR) particles released from a firearm at the time it is discharged may be deposited onto nearby surfaces including the hands and clothing of the shooter and any bystanders. This study measured the relative amount of GSR detected on the shooter and on three bystanders in close proximity. Test-firings were conducted in duplicate using five different handguns with ammunition containing conventional lead, barium, and antimony based primers. Samples were collected from the right hand of the shooter 15 minutes after discharge. Bystanders were sampled 15 minutes after discharge and 2 hours after the initial sampling. A scanning electron microscope with an energy dispersive X-ray detector was used to analyze the samples. A high variability of GSR deposition was observed between firearm/ammunition combinations and between replicate firings. In some instances bystanders had similar concentrations of GSR on their hands to the shooter, making it impossible to distinguish between the two on the basis of particle numbers. Furthermore, after an additional 2 hours, most of the bystanders who initially had GSR particles on their hands had lost them through routine activity. The loss was comparable to what was expected from the hands of shooters based on information published in the literature.

Estimation of the firing distance through micro-CT analysis of gunshot wounds

Estimation of the firing range is often critical for reconstructing gunshot fatalities, where the main measurable evidence is the gunshot residue (GSR). In the present study intermediate-range gunshot wounds have been analysed by means of a micro-computed tomography (micro-CT) coupled to an image analysis software in order to quantify the powder particles and to determine the firing distance. A total of 50 shootings were performed on skin sections obtained from human legs surgically amputated for medical reasons. For each tested distance (5, 15, 23, 30 and 40cm), firing was carried out perpendicularly at the samples using a 7.65-mm pistol loaded with jacketed bullets. Uninjured skin sections were used as controls. By increasing the firing distance, micro-CT analysis demonstrated a clear decreasing trend in the mean GSR percentage, particularly for shots fired from more than 15cm. For distances under 23cm, the powder particles were concentrated on the epidermis and dermis around the hole, and inside the cavity; while, at greater distances, they were deposited only on the skin surface. Statistical analysis showed a nonlinear relationship between the amount of GSR deposits and the firing range, well explained by a Gaussian-like function. The proposed method allowed a good discrimination for all the tested distances, proving to be an objective, rapid and inexpensive tool for estimating the firing range in intermediate-range gunshot wounds.

Gunshot Residue Deposits on the Gas Pistons of Assault Rifles

Abstract A novel technique is presented to determine whether certain assault rifles using gas-cycling have been fired since their last clean-ing. The presence of soot on the head of the gas piston of a weapon allows an examiner to make an estimate of how many times a particular firearm was fired. This is an important observation, as the cleaning of this element is essential to achieve a good operation of the firearm and hence is part of the daily military maintenance. This result is valid for different types of ammunition. The quantity of gun shot residue increases linearly with the number of shots.

Recent developments in the methods of estimating shooting distance.

A review of developments during the past 10 years in the methods of estimating shooting distance is provided. This review discusses the examination of clothing targets, cadavers, and exhibits that cannot be processed in the laboratory. The methods include visual/microscopic examinations, color tests, and instrumental analysis of the gunshot residue deposits around the bullet entrance holes. The review does not cover shooting distance estimation from shotguns that fired pellet loads.

Machine Washing or Brushing of Clothing and Its Influence on Shooting Distance Estimation

Experiments were conducted to assess the effect of machine washing or brushing of clothing items on Gunshot Residue (GSR) patterns (gunpowder residues, lead, and copper, deposits) around bullet entrance holes. Results show that those treatments decrease considerably the amount and density of GSR. However, for close shooting distances not all of the GSR deposits are removed. Remaining patterns may be visualized by specific color reactions and used for shooting distance estimation.

Fundamental Studies of Gunshot Residue Deposition by Glue-Lift

Abstract The mechanism of gunshot residue (GSR) deposition and its probing characteristics have been studied by the Glue-Lift collection of GSR and its identification by scanning electron microscopy and energy-dispersive X-ray analysis (SEM-EDX). By blocking alternately muzzle-blast residues and trigger-blast residues of shotguns, it has been shown that, if the firearm is thoroughly cleaned before the firing, the muzzle-blast residues seldom settle from the air onto the shooter's hands. Whereas the trigger-blast residues are literally blasted onto the immediate surfaces of the firearm and on both of the shooter's hands that are on the weapon. Therefore, the hand deposits are mainly the breech deposits. If the firearm is not pre-cleaned the residues of previous firings lodged as fouling in the interior of the gun are blown off rather irregularly through the breeches and the muzzle in the subsequent firings. These residues occasionally overlap with the fresh breech deposits of the shooter's hands. Color tests for residue developed with sodium rhodizonate have confirmed the basic mechanism of GSR escape through the breeches and the ejection mechanism of the close-breech weapons. The forced deposition of the trigger-blast residues is an advantageous as well as limiting process. The contrast of residue deposits on the back of a hand versus the palm, is due to shadowing of the residue particles by the hand grasp on the firearm. But these particles may also be transferred to the nonfiring hand by contact with a fired gun. Whether it is a handgun or a longarm, if the gun is pre-cleaned and the ammunition and the hand grasps remain unchanged, a fixed amount of residues is deposited per firing on the back of the trigger hand. This deposition, which takes into account all deposited particles containing one, two, and three characteristic elements of GSR (e.g., Pb, Sb, Ba), is a fundamental piece of information helpful for the reconstruction of a shooting.

A note on assessability of firing distance from gunshot residues

The quantitatively measurable evidence on a target (e.g. cloth, skin, etc.) due to bullet impact is the gunshot residue (GSR) deposited around the bullet hole and it is the only material available for extracting any quantitative information about the gun discharge from an examination of the target. At close ranges, the gaseous cloud of GSR particles is directly transported onto the target producing a radial distribution of GSR upto a few centimetres around the bullet hole. Some GSR particles are also captured on the bullet surface and transferred to the target through bullet contact during its penetration. Such bullet-carried GSR is deposited on the target at all ranges, but just around the hole margin. GSR deposits on targets resulting from the above two transfer modes can be distinguished and both processes have been investigated to evaluate the infuence of firing distance on the respective GSR deposits on targets. Two different methodologies have been proposed for close and long range estimations with the aid of GSR measurement. The proposed models are found to give encouraging results when tested against available experimental data.

The Mechanism of Gunshot Residue Deposition And Its Probing Characteristics to Reconstruct Shootings

Gunshot residue (GSR) studies by glue-lift were conducted to determine the mechanism of GSR deposition and its probing characteristics that had been essential to reconstruction of shootings in self-inflicted deaths, and have been immensely useful to interpretation of the GSR distribution on a suspect's or victim's hands.Unlike many solid vapors that grow as various forms of crystals, GSR particles form mainly as spheroids (diameter mainly 0.5-55 μm, Fig.1) by solidification of lead, antimony and barium-containing vapors of melted primer when a bullet is discharged from its cartridge with a firearm. The molten condensate morphologies of GSR when combined with the elemental composition (Pb, Sb, Ba), makes GSR quite distinct from many environmental and occupational particulates, which may contain one or more elements of GSR.