Figure 1
Uniform bullet wipe around the margin of an entrance bullet hole.
Shot was fired from 3.04 m (10 ft) at 90 degrees angle of incidence.
Abstract: This study was conducted to determine the reliability of bullet wipe patterns on cloth targets for use by the investigator in analyzing and reconstructing the events in a crime scene investigation. The study included variables such as ammunition, distance to target, and angle of impact. The study examined the coloration and measurements of the bullet wipes and the effect of the variables tested. Although bullet wipe patterns can assist in reconstructing the events, the investigator should exercise caution when interpreting bullet wipe patterns.
This study was conducted to evaluate the usefulness of bullet wipe patterns in investigations. Bullet wipe is a gray or black ring around the circumference of an entrance bullet hole. It consists of bullet lubricant, by-products of propellant, traces of metal from the bullet, and any residue in the barrel from previous use. Bullet wipe is present on lead and full metaljacketed bullets [1]. Figure 1 illustrates bullet wipe around the margin of an entrance bullet hole. When a weapon is fired from a distance of greater than three feet, there usually will not be any visible gunshot residue on the target’s surface. However, a dark ring around the hole is characteristic of a bullet entrance hole. Bullet lubricant and propellant by-products are wiped off around the margin of the hole as the bullet passes through the target [2]. The sodium rhodizonate test can be used to test the dark gray ring around the hole’s margin for the presence of lead [3]. Even though bullet wipe may be left on materials such as doors, walls, and other solids that the bullet passes through, this study deals only with bullets passing through cloth targets. Bullet wipe patterns can be useful as investigative aids because investigators attempt to reconstruct the sequence of events at a crime scene to identify types of physical evidence that may be present [4]. Also, physical evidence can be used to corroborate or expose deception in statements from suspects or witnesses.
Square cardboard targets approximately 12.38 cm by 12.38 cm (12 x 12 in.) in size and .64 cm (1/4 in.) thick were prepared and covered with 100% white cotton fabric. The fabric was wrapped around the cardboard target, stapled in place, but was not stretched.
A Smith & Wesson, model 686, revolver with a four-inch barrel was used to conduct the test. Because a clean weapon might yield inconsistent results for bullet wipe patterns for the first shots [5], ten shots were fired from the revolver before testing targets to maximize propellant by-products in the weapon’s cylinder and barrel.
The first set of tests was conducted to determine whether bullet wipe coloration on the fabric varies with target distance. A single shot was fired at six distances to determine whether there were any observable differences in bullet wipe coloration. The ammunition used was Winchester .38 Special with a 150-grain lead round nose bullet (RNB). Six distances were tested at 90 degrees to target. They were 1.52 m (5 ft), 3.04 m (10 ft), 4.57 m (15 ft), 6.09 m (20 ft), 7.62 m (25 ft), and 9.14 m (30 ft). Two additional test shots were taken at 9.14 m (30 ft) to determine whether the bullet wipe coloration remained similar. An evaluation of the bullet wipe coloration indicated that the bullet wipe from shots fired from 1.52 m (5 ft) to 6.09 m (20 ft) is darker in color than the bullet wipe coloration from shots fired from farther distances. However, some of the shots that were repeated at 9.14 m (30 ft) did not consistently produce the same color bullet wipe on the cloth. See Table 1 for a summary of bullet color evaluation. See Figures 2 and 3 for examples of bullet wipe color at the same distance. The temperature of the barrel was not measured but there was a delay of several minutes between each test shot to observe and record the results.
The second set of tests was conducted to determine whether bullet wipe measurements on the fabric varies at different distances to the target. The ammunition for this test was Winchester .38 Special with a 150-grain lead RNB. Six distances were tested at 90 degrees to target. They were 1.52 m (5 ft), 3.04 m (10 ft), 4.57 m (15 ft), 6.09 m (20 ft), 7.62 m (25 ft), and 9.14 m (30 ft). A single shot was fired at each distance and two additional test shots were taken at 9.14 m (30 ft) to determine whether bullet wipe measurements remained consistent at this distance. The bullet wipe measurements ranged from 10 mm by 10 mm to 12 mm by 13 mm. See Table 2 for a summary of bullet wipe measurements.
The third set of tests was conducted to determine whether bullet wipe measurements on the fabric varies with four types of ammunition at a specific distance. A distance of 3.04 m (10 ft) was used at 90 degrees to the target to test the ammunition. The ammunition tested included 3-D remanufactured .38 Special with 125-grain semi-wad cutter (SWC), Winchester .38 Special with 158-grain LRN, Precision Made Cartridges (PMC) .357 Magnum with 158-grain jacketed soft point (JSP), and Remington .38 Special with 125-grain semijacketed hollow point (SJHP). Figure 4 illustrates the bullet wipe impressions from four different bullet types. The 3-D remanufactured .38 Special with 125-grain SWC measured 12 mm x 12 mm. The Winchester .38 Special with 158-grain LRN measured 10 mm x 10 mm. The PMC .357 Magnum with 158-grain JSP measured 8 mm x 10 mm. The Remington .38 Special with 125-grain SJHP measured 10 mm x 11 mm.
The fourth set of tests was conducted to determine whether bullet wipe measurements on the fabric varies with different muzzle to target angles. The tests were conducted at a distance of 3.04 m (10 ft) using Winchester .38 Special ammunition with a 150-grain lead RNB. Five rounds were fired into cloth targets positioned at 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, and 40 degrees to the bullets’ paths. Tables 3 and 4 list the average measurements of the bullet wipe patterns. The width of the bullet wipe ranged from 7 mm to 11 mm and the length from 10 mm to 14 mm. Figure 5 illustrates elongated bullet wipe patterns at a 40 degree angle of incidence at 3.04 m (10 ft).
Bullet wipe does not always leave a uniform deposit around the margin of the entrance hole when fired at 90 degrees to the target. Figure 6 illustrates asymmetrical bullet wipe patterns fired at 90 degrees to the target. Therefore, investigators should not assume that the angle of the weapon to the target is greater than or less than 90 degrees based on symmetry. A possible cause for asymmetrical bullet wipe patterns on fabric for bullets fired at 90 degrees could be because the bullet exerted force on the fabric and the fabric gave way at the weakest fibers.
The color of bullet wipe for lead round nose bullets varied with each shot. A possible cause for variations in bullet wipe color could be because of different levels of oxidation on lead bullets or the friction between the fabric and surface of the bullet as it contacted and exited the fabric. Bullet wipe from jacketed bullets was lighter in color around the margin of the entrance hole compared to the color of bullet wipe from nonjacketed lead bullets.
The amount of tension for the fabric on the cardboard forms also produced asymmetrical bullet wipe patterns. The bullet wipe measurements for nonstretched cloth targets were 10 mm x 10 mm and, when stretched tightly over cardboard forms, they were 11 mm x 12 mm. Therefore, the investigator should consider whether the fabric was stretched tightly or loosely when examining a bullet wipe pattern. An asymmetrical pattern may indicate stretched fabric instead of an increased angle of muzzle to target.
Using lead round nose bullets at a distance of 3.04 m (10 ft) for 90, 85, 80, and 75 degrees, the bullet entrance hole averaged 11 mm x 11 mm. At 70, 65, and 60 degrees, the bullet entrance hole averaged 10 mm x 11 mm and was elongated by 1 mm. At 55 degrees, the bullet entrance hole averaged 9 mm x 16 mm and was elongated by 7 mm. At 50 degrees, the bullet entrance hole averaged 9 mm x 14 mm and was elongated by 5 mm. At 45 degrees, the bullet entrance hole averaged 7 mm x 13 mm and was elongated by 6 mm. At 40 degrees, the bullet entrance hole averaged 9 mm x 14 mm and was elongated by 5 mm. The findings indicate that there is a general tendency for the bullet wipe pattern to be elongated; however, specific bullet or target angles cannot be accurately determined on the basis of the elongation of the bullet wipe pattern. In the experiment, the first observable elongation in the bullet wipe pattern occurs at 70 degrees and is elongated by 2 mm. The elongated bullet wipe pattern is not directly proportional to the angle of incidence. As noted in Tables 3 and 4, some increased angles of incidence produce lesser degree of elongation.
The tapered end of the elongated pattern indicates the angle of incidence of the weapon’s muzzle to the target. (Figure 7 illustrates the tapered bullet wipe pattern.) This may be due to the bullet contacting the fabric at an angle and stretching it until the fibers give way. A darker colored bullet wipe was also observed on the opposite side of the angle of incidence at 60, 65, 50, 45, and 40 degrees. Figure 8 illustrates a darker colored bullet wipe pattern on the opposite side of the angle of incidence. This may result from the square area of the bullet’s surface contacting the fabric. Another observation is that the fabric around the circumference of all the bullet holes was turned inward into the cardboard target. This feature is consistent with the direction of travel for the bullets.
Understanding bullet wipe patterns can assist the investigator in analyzing and reconstructing the events in a crime scene investigation. Investigators can evaluate the bullet wipe pattern to determine whether the pattern is consistent with other physical evidence at the crime scene; however, the investigator should exercise caution when interpreting bullet wipe patterns.
| Dark coloration: | Light coloration: |
| 1.52 m (5 ft) | 7.62 m (25 ft) |
| 3.04 m (10 ft) | 9.14 m (30 ft) |
| 4.57 m (15 ft) | 2nd shot at 9.14 m |
| 6.09 m (20 ft) | 3rd shot at 9.14 m |
| Shooting Distance | Bullet Wipe Pattern | |
| 1.52 m (5 ft) | = | 11 mm x 11 mm |
| 3.04 m (10 ft) | = | 12 mm x 13 mm |
| 4.57 m (15 ft) | = | 10 mm x 13 mm |
| 6.09 m (20 ft) | = | 11 mm x 11 mm |
| 7.62 m (25 ft) | = | 10 mm x 10 mm |
| 9.14 m (30 ft) | = | 10 mm x 11 mm |
| 2nd shot at (30 ft) | = | 11 mm x 11 mm |
| 3rd shot at (30 ft) | = | 12 mm x 12 mm |
| Degrees | ||||||
| Shot A | 10 mm x 10 mm | 10 mm x 10 mm | 10 mm x 11 mm | 10 mm x 12 mm | 10 mm x 14 mm | 11 mm x 12 mm |
| Shot B | 10 mm x 11 mm | 10 mm x 10 mm | 11 mm x 11 mm | 9 mm x 11 mm | 11 mm x 12 mm | 11 mm x 11 mm |
| Shot C | 10 mm x 10 mm | 11 mm x 11 mm | 11 mm x 11 mm | 10 mm x 11 mm | 10 mm x 11 mm | 11 mm x 11 mm |
| Shot D | 10 mm x 10 mm | 11 mm x 11 mm | 11 mm x 12 mm | 10 mm x 11 mm | 11 mm x 12 mm | 9 mm x 11 mm |
| Shot E | 10 mm x 10 mm | 11 mm x 11 mm | 10 mm x 11 mm | 11 mm x 12 mm | 10 mm x 12 mm | 10 mm x 12 mm |
| Average Size | 10 mm x 10 mm | 11 mm x 11 mm | 11 mm x 11 mm | 10 mm x 11 mm | 10 mm x 12 mm | 10 mm x 11 mm |
| Shot A | 9 mm x 11 mm | 9 mm x 12 mm | 9 mm x 14 mm | 9 mm x 12 mm | 9 mm x 14 mm |
| Shot B | 10 mm x 11 mm | 9 mm x 12 mm | 10 mm x 14 mm | 8 mm x 12 mm | 10 mm x 14 mm |
| Shot C | 10 mm x 11 mm | 9 mm x 12 mm | 10 mm x 14 mm | 8 mm x 12 mm | 10 mm x 15 mm |
| Shot D | 9 mm x 11 mm | 9 mm x 13 mm | 9 mm x 14 mm | 9 mm x 14 mm | 9 mm x 14 mm |
| Shot E | 9 mm x 11 mm | 8 mm x 13 mm | 9 mm x 14 mm | 9 mm x 14 mm | 9 mm x 15 mm |
| Average Size | 9 mm x 11 mm | 9 mm x 12 mm | 9 mm x 14 mm | 7 mm x 13 mm | 9 mm x 14 mm |
*From the Journal of Forensic Identification Vol. 55, No. 4, July/August 2005
The Official Publication of the International Association for Identification
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