Blank Cartridges

Doubts initially arose about the particle classification scheme when the NIFSL experienced a case involving the examination of a suspect's upper outer clothing for FDR, in which the only discharge particle types detected were lead only and barium, calcium, silicon (the barium, calcium, silicon type was considered to be unique to the discharge of a firearm at the time). The size and appearance of the particles were consistent with FDR residue; however, none of the other particle types were detected and test firing of similar ammunition to that used in the incident (same caliber and head stamp) produced the complete range of particle types. In an effort to explain this anomaly it was decided to investigate the suspect's occupation as a possible source of the particles. Inquiries revealed that the suspect was employed as a general laborer on a building site and that cartridge-operated industrial tools (stud guns) were used on that site. Consequently it was necessary to investigate discharge residue particles from all types of cartridge-operated industrial tools used in Northern Ireland, in order to establish if this was the source of the particles detected on the suspect. The results of the study191 neither proved nor disproved that the use of a cartridge tool accounted for the particles on the suspect, but it did show that the particle classification system needed revision.

Two other similar cases were subsequently experienced and as a consequence it was decided to act on the side of safety by reclassifying barium, calcium, silicon particles as indicative, rather than unique, to the discharge of a firearm.

To clarify the situation and to test the validity of the particle classification scheme it was necessary to consider other possible sources of particles that may have a similar elemental composition and morphology to FDR particles. As the formation of FDR particles involves high temperatures and the particles have the appearance of condensing from a vapor or melt, it was decided to study blank cartridges other than those used in cartridge tools. A very limited range of toy caps, matches, signal flares, and fireworks were also examined as these, when used, involve high temperatures and may contain one or more of the elements lead, antimony, or barium, elements associated with firearms ammunition.

.22" Pb, Sb, Ba, Hg (Al, Cl, Cu, Fe, K, S, Si, Zn)

25 7.65 mm

/KynochN

.455" Colt

/domnionN

^455 Colt/

30 .450" ACP

.380" ^ j Pb, Sb, Ba (Al, Cl, Cu, K, S, Si, Zn)

)MNION\

)MNION\

36 9 mm funis\

37 8 mm

38 7.62 mm

.38" SPL Pb, Sb, Ba (Al, Ca, Cl, Cu, Fe, K, S, Si, Zn)

40 6.35 mm

Figure 19.1 Residue in spent cartridge case (blanks).

A range of blank cartridges were examined to determine the elemental content of the primer. Particular attention was given to blank cartridges designed for use in starting pistols and replica firearms as these sources are the most likely to be encountered in casework. Results are given in Figure 19.1.

/gecoN

Vosy

9 mmP

.303"

.303" Pb, Sb, Hg (Al, Ca, Cl, Cu, Fe, K, S, Si, Zn)

\.32 S&W/ (Al, Ag, Ca, Cl, Cu, Fe, K, S, Si, Zn)

.450" ACP Pb, Sb, Ba (Al, Ca, Cl, Cu, Fe, K, S, Si, Zn)

78 E

figure 19.1 (Continued.)

Note: Comparison of Figure 19.1 with Table 19.1 and Table 19.2 reveals that blank cartridges are similar in composition to live ammunition and may be expected to produce discharge particles with similar composition to those originating from firearm discharge.

Table 19.1 starting Pistol Discharge Residue

Blank No.

Pb, Sb, Ba

Pb, Sb

Pb, Ba

Sb with S Ba Only

Pb Only

1

103

ND

2

ND 2

ND

2

96

14

7

ND ND

ND

3

116

4

ND

5 ND

ND

4

126

8

ND

ND ND

6

5

80

7

8

10 ND

ND

6

133

ND

ND

ND ND

ND

7

99

ND

ND

3 ND

ND = none detected.

table 19.2 Particle types from Promptly Collected FDR

Unjacketed Bullet Jacketed Bullet

.38 Special Caliber .38 Special + P Caliber

Particle Type Number Approximate % Number Approximate %

table 19.2 Particle types from Promptly Collected FDR

Unjacketed Bullet Jacketed Bullet

.38 Special Caliber .38 Special + P Caliber

Particle Type Number Approximate % Number Approximate %

Pb, Sb, Ba

39

17.0

29

27.0

Sb, Ba

None

None

Ba, Ca, Si

3

1.5

None

Pb, Sb

42

18.0

16

15

Pb, Ba

6

3.0

44

40.0

Pb only

138

59.0

14

13.0

Sb only

6

3.0

1

0.5

Ba only

None

4

4.0

Ratio indicative/unique

5:1

4:1

Discharge residue particles from starter pistol blanks were examined for comparison with discharge residue particles originating from firearms ammunition. Table 19.1 gives the starting pistol discharge residue particles classified according to their consistency with FDR particles.

The particles detected were all in the size range 1 to 19 ^m. Both spherical and irregular particles were found and all had the appearance of having partially or wholly condensed from a vapor or melt, and all exhibited some degree of curvature. They did not exhibit any degree of crystallinity and their surface details were smooth, irregular, cratered, or nodular. The physical characteristics of the particles were indistinguishable from FDR particles.

Individually, the starting pistol discharge residue particles could not be distinguished from FDR particles, by physical appearance, by size range, or by elemental composition, which includes the additional accompanying elements. It is a reasonable assumption that discharge residue particles from any blank cartridge could be confused with FDR. Mercury-containing particles could also be produced from the use of blanks incorporating mercury fulminate (see Figure 19.1 for mercury-containing blanks).

When the particles were considered as a group three distinct differences between firearm and starting pistol discharge residue particles were noted.

1. The ratio of indicative to unique particles is markedly different from that of firearm discharge. From firearm residue casework statistics, based on cases with at least one particle in the unique category, the ratio of indicative to unique particles is approximately 35:1. For starting pistol discharge residue particles the overall ratio is in the region of 1:10.

This abundance of unique discharge particles suggests a much more homogeneous mixture of discharge residue, which is not surprising considering that the blanks were rimfire primed; the chemicals are contained within a relatively small volume compared to firearm ammunition, that is, a more intimate mixture contained in a smaller cartridge case. In addition there is no bullet involved to complicate the issue by producing a large number of bullet particles, which would make a substantial contribution to the total number of particles in the indicative category.

It is interesting to note that blank number 6, Table 19.1 produced lead, antimony, barium unique particles only, and also that it had a plastic cartridge case. Considering that eight rounds were fired and that a primer composition consists of a mixture of chemical compounds, this result tends to suggest that the mixture was initially homogeneous and that the discharge gases/vapors were intimately mixed prior to condensation of the particles. This trend is noticeable throughout Table 19.1, particularly for blanks numbered 1, 6, and 7.

2. Unlike FDR, the discharge residue from the blank cartridges contained very few lead-only particles, which is not unexpected as there is no lead bullet involved and any lead-only particles detected must originate from the primer. The few lead-only particles detected all originated from the discharge of blank cartridge number 4. A tentative explanation for this could be the relative proportion/total quantity/burning rate/granulation size of the lead compound or compounds or the degree of uniformity of the priming mixture.

3. Unlike firearm discharge residue, each of the blank cartridges produced a limited range of discharge particle types.

There are several things to be considered when comparing the ratio of indicative to unique particles in firearms casework and starting pistol discharge residue. Like with like is not being compared in that samples of starter pistol discharge residue were taken immediately after firing whereas in casework the vast majority of the suspects were apprehended between 1 and 4 hours after the shooting incident. In laboratory tests one has a high degree of confidence in the origin of the particles in the indicative category, whereas in casework one cannot be sure of the origin of some of the particles,

Table 19.3 Elemental Level Per Particle Type

Particle type

Element

~% Major

~% Minor

~% Trace

Pb, Sb, Ba

Pb

61

39

Sb

39

31

30

Ba

64

31

5

Sb, Ba

Sb

12

88

Ba

100

Ba, Ca, Si

Ba

93

7

Ca

28

55

17

Si

34

52

14

Pb, Ba

Pb

95

5

Ba

38

57

5

Pb, Sb

Pb

66

34

Sb

55

40

5

Sb only

Sb

92

8

Ba only

Ba

100

Pb only

Pb

95

5

particularly the single primary element ones. In order to compare like with like a further experiment was conducted involving promptly collected FDR. Results are given in Table 19.2.

Note: Examination of the copper and zinc relationship revealed that for the unjacketed bullet, 94% of the particles contained copper only and 6% contained both copper and zinc, with copper > zinc. For the jacketed bullet, 90% of the particles contained copper only and 10% contained both copper and zinc, with copper > zinc in 9.5% and copper = zinc in 0.5%.

As can be seen from Table 19.3, the proportion of indicative particles exceeds the proportion of unique particles, even for promptly collected FDR. The higher proportion of indicative particles detected in casework is almost certainly due to particles from nonfirearm sources, particularly single primary element ones, meeting the criteria of the classification scheme.

It is interesting to note that the firing of ammunition with an unjacketed bullet produced more lead-only particles than similar ammunition with a jacketed bullet, which is consistent with the findings of the Aerospace Corporation work.192 A surprising result was the number of particles containing copper from the firing of the unjacketed bullets. This is inconsistent with its findings and is difficult to explain, as the only obvious source of copper is the cartridge case/primer cup. It concluded that these sources did not appear to make a significant contribution to the elemental composition of the discharge particles. Little significance can be attached to this finding as it is based on a particular gun/ammunition combination and very limited experimental data.

Starting pistols/blank firing imitation firearms normally have a hardened steel blockage in the barrel to prevent them from being converted to fire bulleted ammunition. Firearms and firearms ammunition are designed so that the maximum pressure is reached when the bullet has traveled a considerable distance up the barrel (like an expanding chamber). Thus the nature of the discharge process differs between firearms and blank firers and this could account for the homogeneous character of the discharge gases and vapors from blank cartridges. In a firearm the vast majority of the discharge residue emerges from the muzzle whereas blank firers have a small vent, usually at the top, to emit the discharge residue. Because of the smaller fixed volume available to the discharge residue gases and vapors and the venting mechanism in blank firers, it is likely that more uniform temperatures and pressures are attained and better mixing occurs, leading to an abundance of lead, antimony, barium particles and a limited range of particle types.

Whatever the reason, there is no doubt that the discharge of blank cartridges produces a much higher ratio of unique to indicative particles than the discharge of firearm ammunition. As a consequence of the work on blank cartridges, discharge residue particles that were previously referred to as FDR are now referred to as cartridge discharge residue (CDR).

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