Reconstruction of exploded pipe bomb. Reprinted, by permission, from the U.S.  Postal Inspection Service. Copyright 1998 by the U.S. Postal Inspection Service.



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--> Reconstruction of exploded pipe bomb. Reprinted, by permission, from the U.S.  Postal Inspection Service. Copyright 1998 by the U.S. Postal Inspection Service.

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--> 3 Identification Introduction After a bombing takes place, much information about the improvised explosive device can be obtained through careful processing of the bomb scene. In bombing incidents in which black or smokeless powder is used, bomb components recovered may include unreacted or partially burned powder, chemical products of the reaction, and parts of the device, such as the container used to contain the powder, the container used to transport the device, triggering or delay mechanisms, and adhesive tape. Identifying and tracing the origin of these components, including the brand and product line of the smokeless or black powder used in a bombing, may aid in identifying and eventually convicting the bomber. The Committee on Smokeless and Black Powder was specifically charged with determining whether taggants, added to black or smokeless powder, would substantially assist law enforcement personnel in identifying, apprehending, and convicting bomb makers.1 Identification taggants are coded materials that can be added to a product by the manufacturer to provide information that can be ''read'' by investigators at some later stage in the use of the product. Taggants are currently added by manufacturers to a variety of products, such as gasoline, construction materials, and perfume, to enable detection of product tampering or counterfeiting.2 These 1   See Appendix B for the statement of task. 2   Some commercial applications of taggants for prevention of counterfeiting and for product identification are given by Schlesinger (1998).

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--> commercial examples may provide useful guidance regarding addition of taggants to smokeless or black powder, although their information content is limited (they need only be identifiable) and they are not designed to withstand explosions. As a first step in assessing the value of adding taggants to black or smokeless powder, current investigatory methods used by law enforcement personnel are summarized, especially the role of physical evidence in bombing cases. Methods for identifying the powder used in a bomb, such as the use of powder databases, as well as the ability to trace black or smokeless powder from manufacturer to last legal purchaser, have implications that will affect the decision to add taggants. If taggants are to be effective, they must substantially enhance the steps in an investigation and lead to faster apprehension and more certain conviction of the perpetrators. An additional factor is the nature of the taggant itself. The committee found it helpful to list criteria for an ideal taggant, not only to assess the state of current technology but also to provide guidance for design of new taggant technologies. Currently, Switzerland is the only country where taggants are added to explosives. This program includes the tagging of black powder, but only that used for blasting purposes. Neither smokeless nor black powder for shooting purposes is tagged. The relevance of the Swiss experience has been carefully assessed in considering the addition of taggants to smokeless and black powder in the United States. Methods and Approaches The Role of Physical Evidence in Bombing Cases The utility of adding taggants to propellant powders rests on the incremental benefits they may offer to law enforcement in the context of all the physical and chemical evidence available in a given case. A primary focus of forensic laboratory examination of postblast evidence is to analyze chemical residues in order to identify the explosive and provide investigators with as much information as possible about its probable origin. Identifying the explosive, however, is but one part of a comprehensive examination process; to better understand the scope of such an investigation, it is instructive to examine typical components of an improvised explosive device and the nature of evidence left after an explosion. A smokeless or black powder improvised device consists of a number of components, including some or all of the following: powder, a container to confine the powder, delivery and concealment means (bag, parcel, and the like), an ignition mechanism, and a timing or victim-initiated mechanism (see Figure 3.1). Other sources of physical evidence can include material designed to injure or kill (e.g., nuts and bolts, screws, nails, and metal staples) and packaging material (e.g., wood or cardboard boxes). Such components can result in potentially valuable physical evidence being recovered at the crime scene; examples include

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--> Figure 3.1 Pipe bomb.  SOURCE: Adapted from Scott (1994). fragments of the container, unburned powder, pieces of the packaging, lengths of safety fuse, wires, springs, initiators, fragments of batteries, fragments of clocks, and the like. Any of the components of an improvised explosive device potentially may be used to associate the device with its builder. One example is the specialty nails recovered at the scene of the Centennial Park bombing. Approximately 6 pounds of 8d nails, called "concrete" or "masonry" nails, were used in the bomb. Both the type of nail and the amount purchased were unusual. As a result, the Federal Bureau of Investigation (FBI) requested that individuals with knowledge of such a purchase contact the FBI.3 Propellant powders are normally designed to function by very rapid burning rather than by detonation. Frequently, unreacted smokeless powder granules are thrown out of an exploding device and can be recovered at the bomb scene. Less often, unreacted black powder can be located similarly, but characteristic residue is nearly always present after black powder bombings (in the absence of water). Information about the powder used in a bomb supplements the data about the 3   FBI press statement, November 18, 1997.

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--> many other kinds of physical evidence typically present at a bomb scene to assist investigators in identifying a suspect and linking the individual to the crime. Black Powder Unreacted black powder consists of irregularly shaped granules coated with graphite, giving the granules a distinctive black and glossy appearance when observed through a microscope. As discussed in Chapter 1, the typical composition contains charcoal, sulfur, and potassium nitrate (or occasionally sodium nitrate). Black powder is not a very efficient explosive in that a large percentage of its products are condensed solids rather than gases (AB Bofors Nobelkrut, 1960). This does, however, give forensic scientists an advantage in that black powder, even if entirely consumed, yields significant quantities of characteristic residue (Mohanty, 1998; Bender, 1998). The primary intrinsic characteristics of black powder are its morphology, composition, and the large quantity of residue produced by burning or explosion. Smokeless Powder Only single-and double-base smokeless powders (see Chapter 1) are normally encountered in explosive devices.4 As noted previously, smokeless powders contain small amounts of chemical additives, such as stabilizers or flash suppressants; these substances may be identified during the postblast chemical analyses of powders or residues. Smokeless powders generally have a graphite surface coating and are produced in more regular shapes than black powder. Common shapes include flattened balls, tubes, and disks. An important part of the forensic examination of smokeless powders involves the careful measurement of the granule dimensions (Figure 3.2) either with a microscope equipped with a calibrated micrometer eyepiece or an image profiler. Recently, the National Laboratory Center of the Bureau of Alcohol, Tobacco, and Firearms (ATF) has begun to explore the use of digital image capture and digital image analysis to replace these labor-intensive ways of measuring granule dimensions (Bender, 1998). 4   Only single-and double-base powders are available commercially; triple-base powders and composite propellants are manufactured for special applications, such as large-caliber military weapons or air-bag inflators.

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--> Figure 3.2 Physical characteristics of various types of smokeless powder.  SOURCE: Adapted from Bender (1998). Use of Black and Smokeless Powder Databases The FBI Chemistry Unit Laboratory and the National Laboratory Center of the ATF have each devoted considerable effort to accumulating data on the physical dimensions and chemical composition of different types of smokeless powders (see Appendix F) for use in forensic investigations to identify smokeless powder. The creation and maintenance of these two powder databases require the commitment of laboratory resources to accomplish a variety of tasks: liaising with powder manufacturers and distributors to obtain samples of new products, accumulating samples of different lots of powder, analyzing physical dimensions and morphologies of the smokeless powder granules, analyzing the chemical composition of representative samples of the smokeless powders, and entering these data into a computerized powder database (Wallace and Midkiff, 1993; Bender, 1998). Because of the pressure of casework and the limited human and financial resources available for this activity, the powder databases maintained by the FBI and ATF are incomplete.5 5   Personal communication, Cynthia Wallace, ATF, March 19, 1998, and Ron Kelley, FBI, March 19, 1998.

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--> Although both the FBI Chemistry Unit Laboratory and the National Laboratory Center of the ATF are able to identify the type of smokeless powder used in a bombing or in an unexploded device in the majority of cases, both laboratories nevertheless do encounter smokeless powder samples that are not in their powder databases. In such cases, valuable time may be lost at the beginning of an investigation because of the need to visit powder manufacturers to solicit their technical staffs' assistance in identifying the powder. In some cases, the origin of the smokeless powder used in a bombing or attempted bombing may remain undetermined. Analysts at both the FBI Chemistry Unit Laboratory and the National Laboratory Center of the ATF expressed the belief that the addition of taggants could aid them by providing the ability to identify the manufacturer and product line of a smokeless powder, especially in those instances in which conventional analytical methods now fail.6 In forensic investigations of black powder, the granule size is the main characteristic examined.7 The FBI and ATF keep samples and/or information about the physical dimensions of various commercially available black powders. These samples and data are available for use in comparisons with evidence from bomb scenes. Both agencies agreed that information about the chemical composition of the different black powders has little evidentiary value. Tracing the Product Through the Distribution Chain Taggants may be used to identify the manufacturer and product line of smokeless or black powder used in a bomb without additional record keeping on the part of the manufacturer or retailer. For example, the dyed powder granule that Alliant Techsystems adds to some of its smokeless powder allows the user to identify immediately the specific product line (Red Dot, Blue Dot, Green Dot). However, establishing an additional audit trail would be necessary to enable law enforcement personnel to trace a particular powder used in a bomb from the manufacturer to the last legal purchaser. At each stage in the distribution system, sellers would have to record which tagged powders were sent to which customers, and retail outlets would have to keep their sales records in a form that could be readily accessed by investigators. To examine the issues raised by such a record-keeping system, the committee reviewed the existing system of normal business records kept in the manufacture, distribution, and retail selling of powders.8 Three types of records could be kept in the current system: records within 6   Site visits to the ATF and the FBI (see Appendix F) and subsequent discussions with laboratory personnel, August 19, 1998. 7   Personal communication, Cynthia Wallace, ATF, June 24, 1998. 8   For the purposes of this study, analysis of record keeping was limited to black and smokeless powder sold commercially for reloading purposes. Other applications of black and smokeless powders include use in commercial ammunition and specialized military devices, among others. However, the volume of production for commercial ammunition is tremendous, and the array of military

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--> a manufacturing or distribution facility, records tracking the movement of powder between such facilities, and records at the retail level that identify the purchaser. Current Record Keeping in the Powder Distribution System Details of the record-keeping process were provided by a company that both packages its own powder and repackages powders made by other companies;9 the record-keeping procedures were not expected to vary widely throughout the powder industry. In repackaging powders, each 1-pound (or larger) canister of powder is stamped with a date of packing and a lot number. This stamp also goes on the packing boxes that hold the powder containers. Records of the amount packaged, date, and lot number are maintained indefinitely. However, once the powder is shipped from the repackaging facility to either master distributors or retailers, the chain of record keeping ends, and a record of the final destination of the canisters packaged on a given day from a specific lot does not exist. At the next level of the distribution system, master distributors receive powder from the original manufacturers or repackagers and supply it to smaller distributors and retail outlets (see Figure 1.1 in Chapter 1). Again, records are maintained by the master distributors about the type and quantity of powder on their property, but distribution beyond their facility is not tracked.10 For comparison, the system for tracking high explosives in the United States is more rigorous. In the United States, packaged commercial high explosives are required to be marked with a bar code that indicates the manufacturer and the date and shift on which the explosive was manufactured. These date and shift codes have proven to be useful both in tracing the disposition of purchased explosives and in investigating attempted bombings involving these packaged explosives. Sometimes these packaging markings survive a bomb blast.     applications for black and smokeless powders is immense. As a result, tracking the disposition of a specific lot of powder through the distribution system to the final use of the ammunition or military device would be very difficult. In addition, the relatively high cost and difficulties involved in obtaining quantities of black or smokeless powder sufficient for use in an improvised explosive device from military devices or ammunition also remove these sources from the main focus of this study. 9   Information supplied to the subcommittee during its visit to Hodgdon Powder Company; see Appendix F. 10   When large quantities of black or smokeless powder (over 100 pounds) are transported, the powder is shipped as an explosive, and Department of Transportation regulations require more detailed documentation about the shipment. These records might be helpful in tracking the location of black powder, but they are not currently coupled with the record-keeping procedures within individual manufacturing, packaging, or distribution facilities. Smaller quantities of black powder and most smokeless powder are shipped as flammable solids and are subject to less strict federal regulations.

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--> Current Record Keeping at the Retail Level One potential advantage of a tagging program would be to enable investigators to obtain information leading to the last legal purchaser of the tagged powder used in a bombing. This would require that retail outlets maintain records of which customers purchased which tagged powders. Even in the absence of a tagging program, however, several forensic investigators contacted by the committee indicated that it would be useful in bombing investigations to be able to obtain from local retailers a list of individuals who had recently bought the same type of powder used in the bombing.11 The committee therefore attempted to characterize the current state of record keeping for the retail sale of powders. Federal Requirements Retail purchases of black powder are not regulated for quantities below 50 pounds (Code of Federal Regulations, 1981). Purchases of black powder above 50 pounds are regulated by the ATF in the same way as high explosives: for intrastate or contiguous state use, the purchaser must fill out a form, which is retained by the seller. For interstate transport and use, the purchaser must have a federal license or permit. There are no federal regulations concerning the retail sale of smokeless powders. State and Local Requirements Many states have legislation that regulates the purchase or possession of explosive materials, but the great majority have exempted from licensing requirements small amounts of black or smokeless powder, or all black and smokeless powder that is acquired for personal or recreational use (see Appendix H on state laws). Five states have regulatory legislation that places some restrictions on the purchase of small quantities of black or smokeless powders. California has by far the most detailed scheme.12 Three other states, Illinois, Massachusetts, and Michigan, and the District of Columbia require some form of license in order to purchase, possess, or reload powder.13 Mississippi and Virginia require some record keeping on the part of the sellers.14 Although there is no way of knowing the impact of such controls on potential bombers, the committee is aware of anec- 11   Personal communication from Richard Strobel and Cynthia Wallace, ATF, during a site visit to the ATF National Laboratory Center, March 19, 1998. See Appendix F for more information. 12   See Cal. Health & Safety Code § 12102.1 13   See D.C. Code Ann. § 6-2341(a); Ill. Ann. Stat. Ch. 225, § 210/1004; Mass. Gen. L. ch. 140, § 131(E); and Mich. Comp. Laws, ch. 140, § 129(C). 14   See Miss. Code Ann. § 45-13-101; Va. Code Ann. § 59.1–138.

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--> dotal evidence that law enforcement investigators visit retail establishments to determine whether there is any record keeping that might provide leads to bombing suspects.15 Implementation of a uniform record-keeping requirement for all states would require action by Congress. Taggants for Black and Smokeless Powders While an initial examination of the current state of the art of forensic investigations of bombings indicates that taggants would assist in such investigations, the effects of adding taggants to black and smokeless powders must be carefully examined. Consideration of the characteristics of an ideal taggant helps to clarify the issues involved. Characteristics of an Ideal Taggant Ideal characteristics are by their nature unattainable, but, by establishing these criteria, proposed taggant concepts may be judged against agreed-upon characteristics. If a significant increase in threat from the illegal use of black and smokeless powder demands quick implementation of a taggant system, reasonable concession may have to be made in the selection of a taggant in order to increase overall public safety. The ideal taggant would have the following characteristics, which are not necessarily of equal importance: No real or perceived health or safety risks. The ideal taggant poses no safety risk. It is inert. It does not in any way affect the normal properties of the energetic material in which it is admixed nor does it adversely affect the health or safety of powder workers, powder users, or the general public. The ideal taggant is fully accepted by the public. In addition to posing no real risks, the ideal taggant has no perceived risks. It is unobtrusive and manifests no inconvenience to the end users of the black and smokeless powders nor to the general public. Wide forensic applicability and utility for law enforcement. The ideal taggant is applicable to all black and smokeless powder threats. It can provide unambiguous, detailed information to law enforcement agents concerning the manufacture and distribution of powders used in a crime. Law enforcement agents with only modest training and relatively unsophisticated equipment can obtain this information. The ideal taggant is not a source of cross-contamination, and its intrinsic value is not adversely affected by other sources of contamination. The ideal taggant would not only be recoverable from unburned powder, but would also survive a blast in which all the powder had been consumed. 15   Personal communication to subcommittee during its site visit to the ATF, March 19, 1998, and to the FBI, March 19, 1998; see Appendix F.

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--> Chemical and physical compatibility with black and smokeless powders . The ideal taggant is compatible with all black and smokeless powders and has no measurable effect on the powder's material properties nor its performance characteristics. For example, the presence of the taggant has no effect on performance, safety, sensitivity, stability, shelf life, or ballistic properties. In all respects, the behavior of a black or smokeless powder with or without the ideal taggant is indistinguishable. No adverse environmental impact or contamination. The ideal taggant does not affect the environment in any way. It has no negative impact on the atmosphere, the soil, the water, or the food chain. The lifetime of the ideal taggant is comparable to the shelf life of the properly stored black or smokeless powder in which it is incorporated. Upon exposure to the elements, the taggant will naturally biodegrade or spontaneously decompose so that there is no environmental accumulation. Low cost to various links in the chain of commerce. The ideal taggant is comparatively inexpensive, representing a small fraction of the total cost of the smokeless or black powder in which it is used. This low cost includes the cost of the taggant itself, as well as all manufacturing, distribution, and tracking costs associated with the addition of the taggant. It is safe and simple to incorporate into production of the powders and has minimal, if any, impact on the production process. In addition, the attendant decoding equipment costs are low enough to be affordable to all law enforcement agencies. No viable countermeasures. The ideal taggant is exceedingly difficult to remove from the powder in which it is incorporated. The tagged smokeless or black powder looks, smells, feels, and behaves materially exactly like the untagged powder. The presence of the ideal taggant can be discerned only with appropriate equipment, but detection does not facilitate its removal from the powder. The information encoded in the taggant cannot be compromised or destroyed. The ideal taggant is not found in nature nor in common usage in industry. The presence of the ideal taggant at a crime scene is unequivocally indicative of the involvement of black or smokeless powders. Unique information that is easy to read. An ideal taggant provides unique information on the manufacturer and chain of custody of each black and smokeless powder in which it is incorporated. Gleaning this information is dependent upon the availability of reading and decoding equipment and applicable powder databases. The ideal taggant can provide useful information to each level (field to laboratory) involved in a forensic investigation. Taggant Technologies A large number of companies and other organizations proposed taggant concepts that were considered by this committee (see Appendix D). One of these taggant technologies (the 3M-type taggant) has been used since 1981 in explo-

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--> TABLE 3.3 Level of Current Capability in Chemical and Physical Analysis in a Forensic Investigation and the Incremental Value of Taggants   Capability with Current Forensic Methods (without Taggants) Task For Black Powder For Black Powder Replicas For Smokeless Powder Incremental Value of Taggants Identification of powder materiala Burnedb High—characteristic inorganic residue usually precentc Low to moderate—decomposition powders have characteristics similar to those of pyrotechnic compositions Not identifiable—combustion products are gases May be high if taggant survives and no residue is recovered Unreacted Readily identifiable Readily identifiable Readily identifiable Low—information usually available without taggants Identification of manufacturer of powder material Burned Low—inorganic residues only Low—inorganic residues only Not identifiable—combustion products are gases May be high if taggant survives Unreacted Moderate—unburned black powder from the one U.S. manufacturer and some foreign manufacturers can be differentiated Moderate to high—relatively few manufacturers, and powders tend to contain characteristic additives High—powder size, morphology, and composition point to manufacturer Moderate for black powder and replicas; lower for smokeless powder as information is already available

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-->   Capability with Current Forensic Methods (without Taggants)   Task For Black Powder For Black Powder Replicas For Smokeless Powder Incremental Value of Taggants Identification of product line/type (granulation or designation) Burned Low—inorganic residues only Low—inorganic residues only Not identifiable—combustion products are gases May be high if taggant survives Unreacted Moderate—mesh size provides some information Moderate—mesh size and chemical composition can provide useful information Moderate—can distinguish between ball, flake, and extruded; more difficult to differentiate within these categories Moderate to high—could identify product types if not already known a Ability of chemical analysis to distinguish between smokeless powder, black powder, and black powder substitutes. b Burned powder refers to the products resulting from deflagration of a powder in an explosion and excludes traces of unburned powder. This is an unlikely scenario, especially for smokeless powder, since unreacted powder is recovered or no solid combustion products remain. Further assumptions are made that no residue would have been dissolved by water or destroyed by fire. c Although inorganic ions found in burned black powder are common in the environment, their high concentration at a bomb scene would be characteristic of burned blacked powder. SOURCE: Adapted from information received on site visits by the committee (see Appendix F), presentations of law enforcement and forensic personnel, and Bender (1998).

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--> TABLE 3.4 Capability of Law Enforcement to Trace a Known Powder Used in an Improvised Explosive Device Task Current Capability Capability with Adding Record Keeping Only Capability with Adding Taggants Only Capability with Adding Taggants and Record Keeping Identify a lot or batch Low Low Low High Identify distribution chain Low Low Low High Identify last legal purchaser Low (moderate in significant cases where a large effort is made to investigate retail outlets) Moderate—depends on the volume of sales of the powder Low High Trace the powder in a bomb to possible suspects Low (moderate in significant cases where a large effort is made to investigate retail outlets) Moderate—effective if bomber is the last legal purchaser, no aid otherwise Low Moderate Obtain supporting evidencea Low to moderate—value depends on frequency of specific powder use Moderate—could aid in identifying the time of powder purchase with respect to time of bombing Moderate to high—value depends on frequency of taggant code change High—record keeping may not be necessary if taggant code is sufficiently specific a Represents the utility of record keeping and/or taggants in strengthening evidence linking powder in a known suspect's possession with that used in a bomb.

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--> to identify black or smokeless powder is compared with the incremental value of adding taggants in Table 3.3. In Table 3.4, the incremental value of taggants is indicated in light of the increased ability to trace a particular powder from the manufacturer to the last legal purchaser. Implications of Taggant Use for the Analysis of Black and Smokeless Powders The incorporation of taggants in black and smokeless powders could affect the standard analytical procedures currently used by forensic scientists. An established minimum amount of taggant would have to be found to allow scientists to be sure that the presence of the taggant was not a result of some kind of contamination (at the manufacturing, environmental, or evidence-collection stages). This minimum amount would depend on the taggant type, the amount of taggant per pound of powder, and the frequency with which the taggant was changed. For example, in the case of the multilayer acrylic particle (Microtrace) taggant, the Aerospace report (1980) established that 20 particles should be found at the bomb scene to ensure statistical accuracy of their presence. In Switzerland, law enforcement personnel must find 10 like-coded taggants in order to declare the use of a tagged explosive material in the exploded device (Schärer, 1996). In U.S. courts, it is highly probable that conventional analysis would be required to supplement taggant-based evidence and to negate arguments about contamination. If visible taggants were used, a microscopic analysis might suffice to identify the taggant's presence and decode its information without resorting to detailed chemical analysis. If a taggant were used that was too small to be seen, the microscopic examination of debris and dirt would have to proceed as it would in the absence of taggant analysis to ensure the recovery of significant items of evidence. The search for and analysis of small (molecular-level) taggants could then probably proceed using one of the methods currently employed in the identification and analysis of untagged black and smokeless powders. Table 3.3 indicates what are believed to be the levels of success of current forensic techniques in addressing the different aspects of an investigation of powder used in an improvised explosive device, as well as the committee's judgment about the incremental potential of taggants to increase this capability. Unfortunately, neither the ATF nor the FBI maintain statistics on the solve rate of criminal bombings, and so it is difficult to evaluate quantitatively the potential of taggants to increase the solve rate. Swiss authorities have claimed that in cases where taggants are recovered at the scene of a bombing, the solve rate is higher than in cases where no taggants are recovered.34 34   The solve rate in cases where taggants have been found was 44.4 percent, compared to 16.2 percent when no taggants were found (NRC, 1998). The committee notes that factors other than the presence of taggants have influenced these statistics.

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--> Matching the Bomb Filler to Materials in a Suspect's Possession As noted earlier, many items of physical evidence, including unconsumed powders, containers, batteries, timing devices, tape, and so forth, typically survive a bomb blast. These may be used by investigators to connect a series of incidents or help identify the perpetrator if they can be matched to similar items proven to have been acquired by a suspect or matched to items found in the suspect's possession. This latter match is possible only if a suspect has already been identified and a search warrant obtained. Taggants recovered at the bombing scene would provide an additional piece of evidence that could help connect serial bombings or provide a match with similar taggants in powders in the suspect's possession. The more specific the taggant, the greater its utility for these purposes. As noted in Table 3.3, using taggants to match bomb filler material to materials in a suspect's possession, unlike tracing a particular powder through the manufacturing and distribution process, is, independent of additional record keeping. The data in Tables 3.3 and 3.4 indicate that current methods and techniques of forensic analysis of unburned smokeless powder or black powder residues recovered at the scene can be very helpful in determining the filler type, manufacturer, and even the product type, especially for smokeless powders. However, such recovered powders are by themselves of little value in identifying the last legal owner of the powder or in connecting the bomb to a particular suspect. Correspondingly, the incremental value of taggants is moderate for identifying the manufacturer and product type. The incremental value is relatively high for establishing the chain of possession of the powder if a record-keeping system is instituted with the taggant system, and the increase in the ability to link a particular bomb to a particular suspect is also high with either a record-keeping system or by using a sufficiently specific taggant code, While Tables 3.3 and 3.4 indicate that taggants could have law enforcement benefits, at least in certain cases, there is a lack of data on both the costs and benefits of a tagging program that make a quantitative analysis impossible in the absence of further research. On the cost side, there is inadequate information to assess such factors as compatibility, health and safety impacts, and increased costs to manufacturers. On the benefit side, there are no data on current solve rates. Such information about the success rate of investigators in the absence of taggants would provide a baseline for judging the potential incremental value of taggants. Findings and Recommendations The first priority for law enforcement regarding explosive devices is to protect the public by implementing technology that assists in the detection of such devices, thereby preventing bombings and the resulting deaths, injuries, and prop-

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--> erty damage. However, once a bombing takes place, the identification and arrest of a suspect and the successful, efficient prosecution and conviction of the perpetrator become of paramount importance. The rapid apprehension and conviction of individuals responsible for bombings have three potential benefits: (1) once captured and convicted, individuals cannot repeat their crimes, (2) their arrest may deter others from trying similar activities, and (3) the public is reassured that order is maintained in the community. Finding: More than 90 percent of the deaths and 80 percent of the injuries caused by pipe bombs that use black and smokeless powders occur in locations where security screening is not typically present.35 The lack of a viable detection system to screen for or locate explosive devices in these areas underscores the need for technologies that can assist law enforcement personnel in effectively investigating bombing incidents and prosecuting the offenders. Finding: The evidence that forensic investigators often recover at a bomb scene—such as unburned powder from smokeless powder bombs and characteristic residues or unburned powder from black powder devices—can enable identification of the powder manufacturer and product line, thereby assisting in investigation and prosecution. When bomb technicians are examining the evidence from the scene of the crime, all residues and recovered fragments of components from the explosive device are closely scrutinized, because the identification of suspects and the conviction of guilty parties depend on a collection of many types of evidence. Information about the powder is an important component of the evidence. If a suspect is found to own or have purchased the type of powder used in a bomb, that information can be coupled with the suspect's possession of other components used to make the device (the same type of duct tape, wire, piping, and the like) to assist in arrest and prosecution. Therefore, the more detailed the information about the powder used, the more valuable it is as evidence. For smokeless powders, such unreacted powder is almost always found after an explosion, while unreacted black powder and black powder substitutes are recovered somewhat less frequently.36 Currently, forensic scientists study the physical characteristics and chemical composition of unreacted black or smokeless powder found at a bomb scene in order to ascertain if the manufacturer of the powder or the product line can be determined. For black powder, this sort of information is usually 35   See Table 1.4 in Chapter 1 for more information on black and smokeless powder bombings by target. 36   Especially for smokeless powders, the container used in powder-based improvised explosive devices often ruptures before all of the powder has been consumed, and unburned powder is therefore spread among the blast debris.

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--> dependent on the morphology and dimensions of the powder granules, and therefore it is more difficult to determine the specific manufacturer and product type from a small or damaged powder sample. For smokeless powders, information is often obtained from both the chemical composition and the morphology. Consequently, the manufacturer is more readily established, and it is frequently possible to identify the specific product type. Currently, the FBI and the ATF have powder databases containing complementary information about the physical characteristics and chemical composition of commercial smokeless powders to assist in identifying the manufacturer and product line. In addition, these agencies keep samples and/or information about the physical dimensions of various commercially available black powders. Finding: The existing databases of information about black and smokeless powders, although used extensively in bombing investigations, are incomplete. As of early 1998, the powder databases contained information on a significant fraction of the powders commercially available in the United States, but no systematic approach has been taken to developing a comprehensive powder database or to maintaining and updating the current information. In investigations, forensic scientists do encounter smokeless and black powder samples that cannot be matched to samples in their powder databases. RECOMMENDED ACTION: A comprehensive national powder database containing information about the physical characteristics and chemical composition of commercially available black and smokeless powders should be developed and maintained. Such a database would assist investigators in identifying the manufacturer and product line of these powders used in improvised explosive devices. The ATF and the FBI share information contained in their powder databases. A joint database could provide a more efficient and effective tool for law enforcement.37 Such an effort would also be strengthened by a formal program of cooperation with the powder manufacturers to systematically collect product samples and gather official information about chemical composition and analytic protocols. An informal relationship already exists between the manufacturers and the forensic community in which the manufacturers' assistance is readily obtained during investigations of specific samples. Finding: The minimal record keeping currently associated with the sale and distribution of black and smokeless powders does not allow tracing of a specific lot of powder from the manufacturer to the final retailer. At the retail level, there 37   In addition, access to an easily searchable, comprehensive database could provide valuable assistance to state and local forensic investigators.

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--> is no uniform, comprehensive system for keeping records of sales of powders; current practices vary from state to state, and there are relatively few locales in which any registration occurs. In general, record keeping within the manufacturing facilities is comprehensive, but once a lot of powder has left the plant, it is not possible for the manufacturer to know where a given lot of powder is retailed. At the retail level, some state or local governmental regulations or store policies require the purchaser of black or smokeless powders to sign a register, which is kept by the retailer. Anecdotal evidence indicates that such registers have been used to assist law enforcement personnel in their investigations. However, the costs of such registration systems and the added benefit to law enforcement agents have not been thoroughly evaluated. Today, there are relatively few locales in which registration occurs. The potential value of record keeping is discussed further following the final recommendation of this chapter. Finding: Taggants added to black and smokeless powder and/or an associated record-keeping system could assist a bombing investigation by (1) aiding in the identification of the powder, manufacturer, and product line; (2) aiding in tracing the chain of ownership of the powder to a list of the last legal purchasers; and (3) helping to match the powder used in a bomb to powder in a suspect's possession. A taggant's usefulness would depend on the kinds and amount of coded information it contained; the strength of the audit trail would depend directly on that information and the nature of the system for recording sales. Use of a taggant would require decisions about how much information would be encoded, how often the information would be updated or changed, and whether the taggant and record-keeping costs would outweigh potential benefits. Finding: No tagging system has been fully tested to demonstrate its technical feasibility for use in all types of black and smokeless powders, although in some cases taggants have been added to powders for specific applications. The use of taggants in Switzerland for black powders intended for blasting, and the use of dyed powder grains in some smokeless powder products in the United States, indicate that some forms of taggants are technically feasible for some powder products. However, the suspension of federally funded research on taggants in explosives applications in the United States in 1981 has left many questions unanswered about the compatibility of taggants with the wide variety of black and smokeless powder products currently available.38 Although new taggant 38   The Treasury, Postal Service and General Government Appropriation Bill, 1981 (Committee on Appropriations), Title I, p. 9: "After considering all the factors involved, particularly a Congressional Office of Technology Assessment report, the [House Committee on Appropriations] is concerned that the state of the art in explosives tagging technology is not sufficiently advanced to warrant either implementation or further research and development of this particular program at this time." The committee is not aware of any federally funded research on taggants in explosive materials that has occurred since this appropriations report.

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--> concepts have been proposed that may overcome some of the safety and compatibility concerns raised by the 3M-type taggant currently used in Switzerland, thorough studies have not been performed on the use of any of these proposed taggants in black and smokeless powders. RECOMMENDATION: Identification taggants in black and smokeless powder should not be implemented at the present time. Institution of a taggant program with its associated record-keeping system would incur significant costs. At the current threat level of fewer than 10 deaths and 100 injuries per year and very few terrorist incidents, the committee believes that benefits are not sufficient to justify a tagging program. If the threat increased substantially in the future, and test data were available, benefits might exceed costs, and a tagging program might be warranted. A taggant program for black and smokeless powders would be justified only if three criteria were met: the frequency and severity of black and smokeless powder bombings were found to be high enough to justify tagging, the taggants first were thoroughly tested and found to be safe and effective under conditions likely to be encountered in the legal and illegal uses of the powders, and the benefits to society of taggants were found to outweigh the costs of their use. Since no tagging system has been fully tested to demonstrate its technical feasibility, it is not practicable to tag at this time. RECOMMENDED ACTION: Research should be conducted to develop and test taggants that would be technically suitable for inclusion in black and smokeless powders should future circumstances warrant their use. Although the committee believes that the current level of bombings using black and smokeless powders does not warrant the use of taggant technology, the situation could change for the worse in the future. If policymakers decide that the level and type of bombings require action to increase the tools available to help the investigators of bombing incidents, more needs to be known about what technologies would be helpful. Research needs to focus on discovering and testing taggant concepts in the context of the ideal taggant criteria described by the committee in Chapter 3 and in the context of the capabilities of the forensic community to identify untagged powders. The development and use of a comprehensive database of powder characteristics would help clarify the current scientific capabilities for the identification of untagged powders and focus attention on situations in which increased information from powder mixed with taggants would be helpful. RECOMMENDATION: If the type or number of bombing incidents involving black and smokeless powders increases in a way that leads policymakers

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--> to believe that current investigatory and prosecutorial capabilities must he supplemented, the committee recommends that use of taggants, additional record keeping, or a combination of both actions be considered, provided that the chosen taggant technology has satisfactorily met all of the appropriate technological criteria. Research on taggants, as recommended above, is therefore essential to develop options and demonstrate the technical viability of any taggant system that may be considered for implementation at a future date. The response to an increased bombing threat would depend on the nature of these bombings and the state of the technologies available when the decisions were being made. The type of taggant program and/or level of record keeping could be chosen to reflect the threat that these measures were meant to counteract. Any tagging or record-keeping action considered would have to be evaluated in light of the costs and benefits associated with that particular option. Additionally, if legislation mandating tracking of powders through the retail distribution system were to be enacted, the potential for bombers to use powders from the military or from ammunition to circumvent the record-keeping system would have to be considered. The use of taggants without an associated record-keeping system could help forensic scientists identify the manufacturer and product line of a powder from a bomb or it could be used to match powder recovered at the scene to powder in a suspect's residence or possession. Record keeping could be used in the absence of a taggant program to track a powder type through the distribution chain, which could give law enforcement personnel information about where the powder was sold, and registration of sales at the retail level could help build a list of purchasers in the area near the site of a bombing. The features of a combined taggant and record-keeping program would depend on the level of information in the taggant, the extent of the record keeping, and the degree of coordination between the two. Both of the sample tagging and record-keeping schemes described above, as well as record keeping alone, would aid investigators in demonstrating probable cause in order to obtain a search warrant and access to a suspect's residence, vehicle, and so forth. All of the potential actions listed above would provide additional evidence that would assist in the prosecution of a perpetrator.

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