Bullet Hole Perimeters

The sodium rhodizonate test for lead197 is routinely used in many forensic laboratories for confirmation of bullet damage and range of fire determinations. In a number of cases the test failed to indicate the presence of lead on the perimeter of holes that had a distinct bullet wipe. The bullets involved in these cases were all copper jacketed (FMJ). As the test is routinely used in this laboratory, the negative findings from known bullet holes caused concern. It was decided to instigate a project to assess the reliability of the sodium rhodizonate test for lead, and the validity of lead as an indicator of bullet damage. Also investigated was the bullet wipe pattern for shots fired from different angles, and the dependence of close range residue patterns on the ammunition used.

The first test involved single shot firings at a fixed distance, using the same gun and ammunition type, but varying the angle of the target and the angle of the firer to the target. A "straight on" (0°) shot will produce a uniform circular hole and wipe, whereas a shot fired from an angle will produce an elongated bullet wipe and a somewhat irregular hole. One of the questions to be tested was "does the size and position of the elongated wipe reliably indicate the angle of fire?"

Test results revealed that 62 of the 63 bullet hole perimeters gave a positive rhodizonate test for lead and it was concluded that the size of wipe produced by the bullet increases as the angle of fire increases, for example, a shot fired from 75° (left or right) will produce a larger wipe than a shot fired from 30° (left or right). Shots fired straight on at the target only produced an elongated wipe whenever the target was tilted.

There was a definite tendency for the size and position of the wipe to be reproducible for repeated firings under identical conditions, but in a few instances it varied markedly, without apparent reason. As the size and position of the wipe depends on the relative positions and attitudes of the firer and target, any conclusions about the direction of fire need to be very carefully considered.

The second test involved a series of single-shot close range firings using a revolver, a pistol, and a rifle, but varying the ammunition used. The objective was to determine the influence of the type of firearm and the type of ammunition on the muzzle blast residue pattern deposited on the target in close range shootings.

Results indicated that in each case the diameter and density of the unburned propellant patterns were similar using the same gun but different ammunition. There were variations in the soot (blackening) deposits with different ammunition. Contact shots were very similar irrespective of the ammunition. All gave positive rhodizonate tests for lead.

Although it is always desirable to use the actual gun and the same ammunition type to do range tests for comparison with casework items, if the ammunition type is unknown and the firearm type is known, it is still possible to give a reasonable estimate of range. If both the gun and ammunition type are unknown, that is, at one extreme it could be a low power handgun and at the other it could be a high power rifle, then in these instances it is possible to state only that there is evidence of a close range shooting, give the upper limits for a handgun and a rifle, and then give a rough estimate for each couched in terms such as "not more than" and "not less than."

A final test was conducted to determine the reliability of the sodium rho-dizonate test as an indicator of bullet damage. This revealed that approximately 99% of the ammunition used in the pistols and revolvers gave positive rhodizonate tests on the perimeter of the bullet hole and approximately 94% of the ammunition used in the rifles gave positive rhodizonate tests. These results indicate that the sodium rhodizonate test for lead is reliable and that lead is a good indicator of bullet damage and close range shootings. The results are better than those experienced in casework because, in casework, many bullet hole perimeters are bloodstained and the blood could disturb the perimeter residues and have a masking effect, thereby hindering the removal of residue for testing. Despite this the test is effective for the vast majority of cases. The lower success rate with rifles is difficult to explain, but may well be a result of some of the lightly adhering residue on the bullet surface being lost due to the higher velocity (wind disturbance) before the bullet strikes the target.

Alternative tests for the identification of bullet holes and testing for close range shooting will need to be devised as the use of lead-free ammunition increases.198

Tests were also conducted to determine if it was possible to identify the bullet jacket material from examination of the bullet hole perimeter. The ammunition used is given in Table 20.12 and the test results are presented in Table 20.13.

The residue on the surface of a discharged bullet appears to originate from the base of the bullet itself, from the primer, and from inorganic additives to the propellant. Firings numbered 8, 21, 34, and 35 had lead-free primers yet lead was detected on the perimeter of the bullet holes. Ammunition with barium-free primers gave barium on the perimeter.

Only one of the two nickel-jacketed bullets, number 43, gave nickel on the perimeter of the bullet hole. Nickel was frequently detected from non-nickel-coated bullets. This is a surprising result which demonstrates that the presence of nickel cannot be used to identify the use of a nickel-jacketed bullet. The origin of the nickel is unknown but it may have originated from the primer cup coating.

Table 20.12 Bullet Hole Perimeter Test Ammunition

Test No.

Ammunition

Primer

1

9 mmK Hirtenberg

Ni Jkt FMJ

Pb, Ba

2

9 mmK Sako

Cu Jkt FMJ

Pb, Sb

3

9 mmK W-W

Cu Jkt FMJ

Pb, Sb, Ba

4

9 mmK Federal

Cu Jkt FMJ

Pb, Sb, Ba

5

9 mmP VPT42

Cu Jkt FMJ

Pb, Sb, Ba

6

9 mmP VPT43

Cu Jkt FMJ

Pb, Sb, Ba

7

9 mmP VPT44

Cu Jkt FMJ

Pb, Sb, Ba

8

9 mmP 11 52

Cu Jkt FMJ

Sb, Hg

9

9 mmP K52

Cu Jkt FMJ

Pb, Sb, Ba

10

9 mmP S044

Cu Jkt FMJ

Pb, Sb, Ba

11

9 mmP GECO 80-59

Cu Jkt FMJ

Pb, Sb, Ba

12

9 mmP Norma

Cu Jkt FMJ

Pb, Sb, Ba

13

9 mmP REM-UMC

Cu Jkt FMJ

Pb, Sb, Ba

14

9 mmP RG55

Cu Jkt FMJ

Pb, Sb, Hg

15

9 mmP D143

Cu Jkt FMJ

Pb, Ba

16

9 mmP RG56

Cu Jkt FMJ

Pb, Sb, Hg

17

9 mmP RG57

Cu Jkt FMJ

Pb, Sb, Hg

18

9 mmP WRA

Cu Jkt FMJ

Pb, Sb, Ba

19

.45 ACP R-P

Cu Jkt FMJ

Pb, Sb, Ba

20

.45 ACP W-W

Cu Jkt FMJ

Pb, Sb, Ba

21

.45 ACP SF57

Cu Jkt FMJ

Sb, Hg

22

.45 ACP WRA. Co

Cu Jkt FMJ

Pb, Sb, Ba, Hg

23

.303 RTL49

Cu Jkt FMJ

Pb, Sb, Hg

24

7.62 NATO RG70

Cu Jkt FMJ

Pb, Sb, Ba

25

.223 HP

Cu Jkt FMJ

Pb, Sb, Ba

26

.223 Norma

Cu Jkt FMJ

Pb, Sb, Ba

27

.223 IV170

Cu Jkt FMJ

Pb, Sb

28

.223 RA69

Cu Jkt FMJ

Pb, Sb, Ba

29

.223 RA65

Cu Jkt FMJ

Pb, Sb, Ba

30

.30MI Norma

Steel Jkt JSP

Pb, Sb, Ba

31

.30MI R-P

Steel Jkt JSP

Pb, Sb, Ba

32

.30MI W-W

Cu Jkt FMJ

Pb, Sb, Ba

33

.30MI W-W

Cu Jkt FMJ

Pb, Sb

34

.30MI VE-F

Cu Jkt FMJ

Sb, Hg

35

.30MI VE-N

Cu Jkt FMJ

Sb, Hg

36

.455 Dominion

Pb unjacketed

Pb, Sb, Ba, Hg

Table 20.12 Bullet Hole Perimeter Test Ammunition

(Continued)

Table 20.12 Bullet Hole Perimeter Test Ammunition

(Continued)

Test No.

Ammunition

Primer

37

.455 Kynoch

Pb unjacketed

Pb, Sb, Ba

38

.455 K62

Cu Jkt FMJ

Pb, Sb, Ba, Hg

39

.357 W-W

Cu Jkt JHP

Pb, Sb, Ba

40

.357 R-P

Cu Jkt JSP

Pb, Sb

41

.357 W-W

Pb SWC

Pb, Sb, Ba

42

.357 R-P

Pb SWC

Pb, Sb, Ba

43

.38 S&W RÎL39

Ni Jkt FMJ

Pb, Sb, Hg

44

.38 S&W Norma

Pb unjacketed

Pb, Sb, Ba, Hg

45

.38 S&W REM-UMC

Pb unjacketed

Pb, Sb, Ba, Hg

46

.38 S&W Browning

Pb unjacketed

Pb, Sb, Ba

47

.38 S&W GECO

Pb unjacketed

Pb, Sb, Ba

Note: See Glossary for firearms/ammunition-related abbreviations.

Note: See Glossary for firearms/ammunition-related abbreviations.

It is interesting to note that in all tests in which mercury was present in the primer, it was detected on the perimeter of the bullet hole. The unjacketed lead bullets all gave a large quantity of lead on the perimeter, although this was not confined to unjacketed bullets. The copper results were similarly confusing.

Overall, the possibility of determining the bullet jacket material from the residue around the bullet hole does not appear to be feasible using FAAS. However, FAAS reliably detects elements associated with firearm discharge on the perimeter of the bullet hole and is a very useful method for confirming bullet damage.

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