Containing the Threat from Illegal Bombings An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors (1998) / Chapter Skim
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3 Taggants for Preblast and Postblast Identification of Explosives
3 Taggants for Preblast and Postblast Identification of Explosives
Pages 72-95
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From page 72... ...
Bureau of Alcohol, Tobacco, and Firearms investigation of a car bombing. Photograph courtesy of the Bureau of Alcohol, Tobacco, and Firearms.
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From page 73... ...
The information encoded in an identification taggant can range from the general to the very specific, including date and shift of manufacture. As the specificity of the taggant coding increases, so also does the taggant's potential forensic usefulness, along with the burden on the manufacturer and the cost to society in general.
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From page 74... ...
To complicate the matter, blasting agents can be made by an individual bomber, which raises the issue of whether tagging the raw material of a blasting agent might also be advisable. If explosive-grade ammonium nitrate were to be tagged, should all forms of AN be tagged regardless of their intended use, since they can also be made into a bomb?
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From page 75... ...
taggant, the only one that has been subjected to an extensive technical evaluation and has a long-term history of use, has been added by the Swiss to a limited line of explosives products for the last 18 years (see Appendix F) .4 Following a period of terrorist attacks in the 1960s and 1970s in western Europe, the Swiss mandated in 1980 that explosives be stored in 3A Westinghouse taggant product, consisting of a mixture of rare-earth compounds in a ceramiclike particle, had a gritty texture that was shown to increase the impact sensitivity of some explosive materials when used without polyethylene encapsulation.
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From page 76... ...
76 CONTAINING THE THREAT FROM ILLEGAL BOMBINGS '............................................................................................................................ B""""""""""""""""""""""""""""""""""""',,,'V'A"""~' ~ Oummary OT tne Iuou ~Tfice of Technology ........................................................................................................
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From page 77... ...
Swiss forensic scientists have developed laboratory methodologies to separate the Microtrace taggants from bombing residue and to identify the codes microscopically (see Appendix F)
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From page 78... ...
. Few of the taggant concepts appeared to be beyond the conceptual stage of development, although one reportedly had been subjected to limited field tests carried out with actual explosives.8 The committee grouped the various identification taggant concepts presented to it as follows: · Particulate taggants incorporating particles of a size visible to the eye or under low magnification, with information coded by layered sequences, chemical composition, ingredient melting points, and other methods; · Isotopic taggants using a molecule chemically identical to a compound present in, or added to, an explosive but also bearing an isotopic label at one or more positions added in parts-per-million concentrations; and · Biological taggants using engineered biological molecules, DNA fragments, or substances incorporating other similar technologies.
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From page 79... ...
For particulate taggants, special consideration must be given to their impact on the stability of nitroglycerin explosives and the use of auger-packing machines. The safety assessment must also include toxicity studies to evaluate skin irritation and hazards posed by inhalation or ingestion of the taggant material.
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From page 80... ...
The analysis in Appendix J shows that cross-contamination should be less serious for tagged packaged explosives than for tagged bulk ammonium nitrate. Forensic Utility Background information supplied to the committee in connection with its scheduled meetings and site visits indicated that taggant information would be only one of several forms of evidence considered in a thorough investigation.
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From page 81... ...
To date, no proposed taggant material other than the Microtrace product has undergone extensive blast survivability testing. To the extent that cap-sensitive high explosives are used as initiators or boosters in large bombs containing blasting agents such as ANFO, a tagged initiator or booster might yield sufficient readable tags in the postblast debris to make the cost and effort of tagging blasting agents unnecessary.
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From page 82... ...
This type of unintended consequence needs to be anticipated before taggants are considered for use. Cost of Taggant Material, Processing, and Record Keeping The costs to industry of taggant implementation must be considered in conjunction with the benefits to law enforcement.
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From page 83... ...
Universal Applicability Because using different taggant types for different classes of commercial explosives could complicate collection, recovery, and analytical protocols, it would be attractive to identify a single taggant that could be applied to all types of explosives. Although chemical and physical differences among types of explosives make this unlikely, the number of unique taggant concepts should be kept to a minimum.
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From page 84... ...
Each of the particulate taggant concepts examined by the committee is believed to persist indefinitely in the environment and could represent a source of contamination for mined products. Environmental persistence could be a serious problem in the case of a tagged material used in large quantities, such as fertilizer-grade AN.
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From page 85... ...
The committee lacked information for assessing the effects of biological taggants on susceptibility to countermeasures or cross-contamination but believes that they would be no worse than with other taggant approaches. Biological taggants appear to require a sophisticated level of analysis, which could have a significant impact on law enforcement forensic procedures.
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From page 86... ...
This experience base enables a more detailed examination of the taggant than was possible for other proposed taggant concepts. Safety in Manufacture and Use The Microtrace taggant has been in use in Switzerland in AN-based explosives, dynamites, and plasticized PETN, materials with which it appears to be compatible, and has not posed toxicity hazards.
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From page 87... ...
Utility for Law Enforcement As pointed out above, testing in the United States and use in Switzerland have yielded some information related to the Microtrace taggant' s utility to law enforcement. The well-known McFillen case of 198116 involved recovered taggant particles that may have played a role in successful prosecution, and the Swiss associate higher conviction rates with recovery of the Microtrace taggant and a related domestic taggant at the crime scene.
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From page 88... ...
The Swiss code identifies the manufacturer and the date of manufacture within a 6-month period. Blast Survivability The blast survivability of the Microtrace taggant has been demonstrated by the Swiss experience and described in the OTA (1980)
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From page 89... ...
taggant used by the Swiss, at a reported cost of $180 per pound, are provided for comparison.l8 As Table 3.1 shows, adding Microtrace taggants to ANFO ($0.15/lb) would increase its cost by 60 percent (for 16-mesh taggant)
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From page 90... ...
LEGAL ISSUES Another important step in evaluating the feasibility and desirability of identification taggants is the extent to which they would create or ameliorate legal problems. Many law enforcement agencies today express frustration over their inability to quickly identify and successfully prosecute criminals who make and detonate bombs.
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From page 91... ...
Given the possible legal challenges to such evidence, there is some question as to whether or to what extent currently conceived identification taggants would assist the criminal justice system in prosecuting criminal bombers (see Appendix G
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From page 92... ...
All types of identification taggants are designed to make it easier for law enforcement officials to identify the manufacturers and sellers of the explosive materials used in bomb blasts. Except for the Microtrace taggant, which has been employed by the Swiss since 1980, there is little evidence of how effective identification tags will be in reconstructing the chain of distribution for any particular explosive product.
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From page 93... ...
Technical criteria must be considered in the evaluation of any taggant concept. These criteria are safety in manufacture and use, effect on the performance of explosives products, utility for law enforcement (including ease of countermeasures, cross-contamination problems, forensic and prosecutorial utility, and blast survivability)
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From page 94... ...
These criteria are safety in manufacture and use, effect on the performance of explosives products, utility for law enforcement (including resistance to countermeasures, lack of cross-contamination, forensic and prosecutorial utility, and blast survivability) , environmental acceptability, immunity from contamination of the mined product, costs (of the taggant material, processing, and record keeping)
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