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Influence of a Guitar Bag as an Intermediate Target on Shotgun Pellet Patterns
Abstract
The results presented in this article demonstrate how a foam-filled double textile layer as an intermediate target in close proximity to the muzzle influences shotgun patterns and therefore shooting distance determinations based on these patterns. The results indicate that, for all shot sizes, the patterns are larger when shots are fired through a guitar bag than when they are fired without an intermediate target. The results also demonstrate the small influence of shot size on the pattern change, for the tested shot sizes.
... The pellet material was presumably lead. Karapirli et al. [11] and Kerkhoff et al. [12] both studied the effect of intermediate targets on shotgun dispersion patterns but also mentioned the effect of pellet size. In the study by Karapirli et al. [11], mean pattern size was measured to be smaller with 3.9 mm pellets than with 2.1 mm pellets. ...
... In the study by Karapirli et al. [11], mean pattern size was measured to be smaller with 3.9 mm pellets than with 2.1 mm pellets. In the study by Kerkhoff et al. [12], mean pattern sizes with 3.5 and 3.9 mm diameter pellets were generally smaller than with 2.5 and 2.9 mm pellets. The material of the shot was lead with both studies. ...
... The total weight of the shot charge was kept identical per study in Refs. [11,12], but the reported weights must be considered nominal values since the studies were performed with factory-loaded ammunition. ...
When reconstructing a shooting incident with a shotgun, the muzzle-to-target distance can be determined by relating the size of a dispersion pattern found on a crime scene to that of test shots. Ideally, the test shots are performed with the weapon and ammunition that were used in the incident. But sometimes examiners will have to resort to alternatives, such as using cartridges of the same brand and type but with another pellet size. For this reason, the relationship between pellet size and shotgun dispersion patterns was studied with both lead and steel shotgun pellets. Cartridges were loaded with identical cartridge cases, powder charges, and wads but with different pellet sizes, below size B. The cartridges were fired, and the dispersion patterns at 5 m in front of the muzzle were measured and compared. The results provide strong support for the proposition that shotgun dispersion patterns with both lead and steel shot increase with decreasing pellet size if all other relevant parameters are kept equal. The results also provide an indicative measure of the magnitude of the effect. Pattern sizes were approximately 1.7 times larger with #9 than with #0 lead shot and 1.4 times larger with #9 than with #1 steel shot. The differences between consecutive shot sizes were generally smaller. This means that cartridges of equal brand and type but with the next nearest shot number can be used for a muzzle-to-target distance determination, keeping the information of the current study in mind in the final interpretation of the results. K E Y W O R D S distance determination, lead shot, pellet size, shooting incident reconstruction, shot pattern, steel shot Highlights • Shotgun pattern sizes tend to increase with decreasing pellet size. • With #9 lead shot, pattern size is approximately 1.7 times larger than with #0 shot. • With #9 steel shot, pattern size is approximately 1.4 times larger than with #1 shot.
... Tests with a shotgun show that shooting through an intermediate target (a foam-filled guitar bag with a double textile layer) results in larger shot patterns. This is important to take into account when using the shot pattern to estimate the shooting distance [127]. ...
This review paper covers the relevant literature on forensic firearm examination from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.
To determine the effect of barrel length on pellet patterns fired by sawed-off shot-guns, 00 buckshot, No. 2 shot, and No. 7J/2 birdshot cartridges were fired from 12-gage single-shot Harrington and Richardson shotguns with the barrel lengths progressively shortened to 152 mm (6 in.). The spread of the 00 buckshot pattern was found to increase as the barrel length of the firing weapon decreased. The spread of the pellet patterns increased or tended to remain constant as the barrel length decreased when other types of cartridges were fired from the shot-guns; this depended on the brand of ammunition.
Three methods of measuring the spread of shotgun pellet patterns for the purpose of estimating the range of fire were applied to a series of 7200 buckshot patterns test-fired at distances ranging from 3.6 to 10.7 m (12 to 35 ft). The methods applied were (1) the 'effective shot dispersion' method of Mattoo and Nabar, (2) a method in which the area of the smallest circumscribed rectangle that will just enclose the pellet pattern is calculated, and (3) an overlay method for determining the radius of the smallest circumscribed circle that will just enclose the pellet pattern. Regression analysis was applied to the resulting measurements of the spread of the pellet patterns. The 'effective shot dispersion' was found to give the best fit to a linear function and the best range-of-fire estimates. The area of the pellet patterns was found to be a quadratic function of the range of fire; this measure of pellet pattern spread was also found to have very large shot-to-shot variations. The square root of the area of the pellet pattern was found to be a linear function of the range and to give acceptable range-of-fire estimates.
A series of shotgun pellet patterns were fired at ranges that varied from 3.9 to 15.2 m (10 to 50 ft) using a 12-gauge cylinder-bored shotgun firing No. 2 chilled shot cartridges. The spreads of the pellet patterns were measured in two ways: the radius of the smallest circle that would enclose the entire pattern was measured with a transparent overlay and the square root of the area of the smallest rectangle that would enclose the pattern was calculated. Linear regression analysis was applied to sets of data for shots at three, five, and nine ranges. For both measures of pattern spread the linear regression gave correlation coefficients greater than 0.99, indicating that a linear relationship existed between the measures of the pattern spreads and the range of fire. The confidence intervals for range-of-fire estimates at the 95% confidence level were calculated for each set of data. As expected, increasing the number of test-fired patterns decreases the confidence interval and so improves the range-of-fire estimates obtained from the test-fired patterns.
This book is generated from the authors' numerous years of conducting courses and seminars on the subject of shooting incident reconstruction. It thoroughly addresses matters from simple to complex in providing the reader an explanation of the factors surrounding ballistics, trajectory, and shooting scenes. 420 pp. Pub. 7/11.
The distribution pattern of pellets due to shotguns is an important criterion for the determination of shooting distance. Many factors affect the distribution range, such as characteristics of the gun, the presence and type of intermediate targets, factors related to distance, and the physical variables of the environment. The aim of the present study is to evaluate the effects of different intermediate targets on the distribution range of pellets from a shotgun. Glass, mica auto glass, tempered auto glass, fibreboard, flat iron, aluminium, and grey cotton fabric were used as intermediate targets. The intermediate target was placed one metre away from the main target and shotgun. The spread of pellets was evaluated on the main target with seven shots by using either cartridge numbers 0 or 9. The spread of pellets was significantly larger in the presence of all intermediate targets tested with cartridge number 9 (p p = 0.33) with cartridge number 0. The distribution range of pellets increased in the presence of intermediate targets. This difference was more pronounced in higher density intermediates. In crime scene investigations, the presence and/or type of intermediate target should be taken into account to make information more accurate.
Intermediate targets cause dispersion of a shot pattern by a ricochet effect. Thus, the intermediate target must have sufficient thickness or tensile strength to slow down the initial group of shot striking the target. Aluminum and steel screen, ordinary window glass, thin cardboard and thin cowhide did not manifest these qualities under the conditions of these experiments.
Relatively little has been published in the world literature on shotgun wound interpretation and ballistics. Since only few medical centers see a large number of shotgun injuries, less experienced examiners may be misled easily hi their interpretation of such wounds, particularly with regard to estimates of distance, with grave implications as to judicial consequences. The peculiarities of the shotgun and the shot shell frequently permit more accurate range estimates than do hand weapons, especially for ranges beyond 1 ft. Choke is the most important variable factor influencing the shot scatter pattern in the average medicolegal case, whereas gauge has little effect on pattern size. The most accurate estimation of range is achieved by test firing the same gun and ammunition at varying ranges to compare the spread with the entrance wound. The wound characteristics largely depend upon the distance. Close range shots make a single punched out entrance hole that increases in size proportionally to the range until individual pellets enter the target. Concomitantly, the internal injuries vary, ranging from complete destruction of the target organ at close range to individual pellet wounds at greater distances. However, it is important to realize that pellet scatter patterns within the body may be similar in diameter in both close range and distant shots. Because of this similarity, estimation of range based upon body roentgenograms has been found to be less reliable than was believed previously and, indeed, may be very misleading. Exit wounds are very rare, even at contact range, and occur only hi tangential shots, when thinner portions of the body are injured, or with the use of large pellets (buckshot).
A Study of Buckshot Patterning Variation and Measurement Using the Equivalent Circle Diameter Method
- R Ernest
Ernest, R., "A Study of Buckshot Patterning Variation and
Measurement Using the Equivalent Circle Diameter Method",
AFTE Journal, Vol. 30, No. 3, Summer 1998, pp. 455-461.
Average Pellet-to-Pellet Distance for Estimating Range-of-Fire in Cases Involving Partial Pellet Patterns
- L C Haag
Haag, L.C., "Average Pellet-to-Pellet Distance for
Estimating Range-of-Fire in Cases Involving Partial Pellet
Patterns", AFTE Journal, Vol. 34, No. 2, Spring 2002, pp.
139-143.
Shotgun Proximity Testing: A Review of the Literature Regarding Muzzle-to-Target Distance Determinations Involving Shotguns
- R G Nichols
Nichols, R.G., "Shotgun Proximity Testing: A Review
of the Literature Regarding Muzzle-to-Target Distance
Determinations Involving Shotguns", AFTE Journal, Vol. 38,
No. 3, Summer 2006, pp. 192-203.
Practical Aspects of Firearms, Ballistics and Forensic Techniques
- V J M Dimaio
- Gunshot Wounds
DiMaio, V.J.M., Gunshot Wounds, Practical Aspects
of Firearms, Ballistics and Forensic Techniques, Elsevier
Science Publishing Co., New York, USA, 1985, ISBN 0-444-00928-0.