Widely used for sport and recreational purposes throughout the United States, black and smokeless powders in the retail market are sold primarily for reloading of ammunition and for use in muzzle-loading firearms, respectively. Large quantities of these powders are also used for military purposes. In addition, smokeless powder is used in ammunition manufactured for civilian use, and moderate amounts of black powder are used for blasting in the mining industry. Besides serving these legitimate purposes, black and smokeless powders can also be used to manufacture improvised explosive devices. Although bombs made from black or smokeless powder are usually small (particularly in comparison to the explosives used in incidents such as the World Trade Center and Oklahoma City bombings), they are the devices most commonly used in criminal bombings (FBI, 1997). Metal pipes are the containers used most often for effective black and smokeless powder bombs, which thus are frequently referred to as pipe bombs.
In response to events such as the 1995 Oklahoma City bombing, the U.S. Congress passed the Antiterrorism and Effective Death Penalty Act of 1996, which mandated a reexamination of the feasibility and desirability of adding markers and taggants to explosives.1 (The National Research Council (NRC)
examined these issues for high explosives in its 1998 report Containing the Threat from Illegal Bombings (NRC, 1998). Black and smokeless powders were explicitly excluded from that study, but a 1997 amendment to the law required that the Treasury Department request a separate study of the technical feasibility of adding markers or taggants to black and smokeless powders. The NRC Committee on Smokeless and Black Powder responded by examining the relevant issues, with the goal of analyzing whether markers and taggants could be added to black and smokeless powders, while considering whether such additions would pose a risk to human life or safety; substantially assist law enforcement officers in their investigative efforts; substantially impair the quality and performance of the powders for their intended lawful use; have a substantial adverse effect on the environment; have costs that outweigh the benefits of their inclusion; and be susceptible to countermeasures.2
From 1979 to 1992 in the United States, the number of reported bombings involving black and smokeless powders approximately doubled (Hoover, 1995). However, between 1992 and 1996 (the most recent year for which data were available to the committee), the number of reported bombings involving these powders leveled off, averaging about 650 per year. From 1992 to 1994 the number of "significant" bombing incidents—defined by the committee as those that resulted in (or, for attempted bombings, had the capability of causing) death or injury or a minimum of $1,000 in property damage—was in the range of 250 to 300 per year.
Two federal agencies gather statistics on bombing incidents in the United States: the Department of the Treasury's Bureau of Alcohol, Tobacco, and Firearms (ATF) and the Department of Justice's Federal Bureau of Investigation (FBI). Each agency maintains separate statistics on bombing incidents, and each distributes its own form for voluntary reporting of incidents by local investigators. Discrepancies between the two data compilations complicate the analysis of the bombing threat.
Of all the approaches to reducing bombing incidents, detection of a bomb prior to explosion is the most attractive, since it provides an opportunity to render the bomb safe before it can cause death, injury, or property damage.
Three scenarios for the detection of bombs were considered by the committee: the portal, in which all people or packages entering an area must pass through a few well-monitored checkpoints (for example, at airports); the suspicious pack-
See Appendix B for a complete statement of task.
age; and the bomb threat, in which there is reason to believe that there may be an explosive device somewhere within a large-area, but its location is uncertain (as occurred in the Centennial Park bombing in Atlanta in July of 1996).
- Portal scenario. Because the powder containers in black and smokeless powder explosive devices must be thick enough to provide the substantial confinement of powder required to produce an effective explosion, they are likely to be visible on standard x-ray images. In addition, metal pipe bombs are readily detected by metal detectors, and dogs can detect a wide range of smokeless powders, black powders, and black powder substitutes and currently can be trained to detect devices containing any type of powder. However, dogs may quickly tire and are not well suited to the task of routine screening of large volumes of material.
- Suspicious package scenario. Portable standard x-ray systems currently used to examine suspicious packages can provide information about the type and location of an explosive device within the package that would assist in disarming the device. Vapor or residue detectors are becoming available that might be used to examine a suspicious package, but the results are likely to be less definitive. Dogs are known to be effective in examining suspicious packages.
- Bomb threat scenario. At present, searching by dogs or bomb squads is the only method for locating a bomb in a large-area. Dogs combine high sensitivity to powders along with independent searching capability and thus enjoy a major advantage over other detection systems in this scenario. All other systems must be close to the device to function properly.
These three scenarios impose different requirements on detection systems. Portal systems are stationary, and so high capital cost may be tolerable if the system has a high throughput and low false alarm rate. In the suspicious package and bomb threat scenarios, system portability and low cost likely are more important. Despite progress in improving the detection of explosive materials with new technologies, current equipment can be expensive and is not always sufficiently sensitive or appropriately configured to detect all types of black or smokeless powder bombs.
The addition of markers to black or smokeless powder would be intended to enhance detection, particularly by low-cost, simple systems. An ideal marker would have the following characteristics: no real or perceived health or safety risks; wide applicability and utility for law enforcement; chemical and physical compatibility with black and smokeless powder; no adverse effect on powder or ballistic performance; no adverse environmental impact or contamination; low costs to various links in the chain of commerce; unique signature impossible to mask or contaminate; unique information that is easy to detect; and an appropriate lifetime.
Although 2,3-dimethyl-2,3-dinitrobutane (DMNB), one of the markers approved for use in plastic and sheet explosives under the International Civil Avia-
tion Organization Convention, best meets the overall criteria for a suitable marker for high explosives, considering its incorporation into powders raises two potential concerns: DMNB is volatile and might evaporate during the typical shelf life of a black or smokeless powder sample; DMNB is also moderately toxic, and so its effects on those exposed to the marked product would have to be carefully assessed.3
The feasibility of detecting a bomb before it explodes depends on the target and the method of delivery. Most deaths and injuries caused by black powder or smokeless powder bombs have occurred in isolated, not public, surroundings,4 and so these bombs were unlikely to have been detected through routine screening procedures. Although wider deployment of routine screening technologies is unlikely to affect significantly the number of victims of black and smokeless powder bombings, improving the capability of law enforcement personnel to deploy bomb detection technologies in response to an identified threat at a given site may still help to prevent casualties among bystanders and bomb squad personnel.
After a bombing takes place, information about improvised explosive devices must be obtained from material recovered at the scene. In bombing incidents in which black or smokeless powder is employed, many items of physical evidence typically survive a bomb blast. These items may include unexploded powder, chemical products of the reaction, and parts of the device such as the container used to enclose the powder, the container used to transport or conceal the device, triggering or delay mechanisms, and adhesive tape. Identification of the nonexplosive bomb components and the type of black or smokeless powder used in a bombing may aid in the identification and eventual conviction of the bomber.
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. If taggants are to be effective, they must substantially enhance the steps in the forensic examination and lead to the faster apprehension and more certain conviction of the perpetrators.
A bomb container filled with black or smokeless powder often ruptures before all of the energetic material is consumed. The result is that unreacted powder, as well as decomposition residues in the case of black powder, can be
recovered at the bomb scene and used in a forensic investigation. Both the FBI Explosives and Chemistry Units Laboratory and the National Laboratory Center of the ATF accumulate data on the physical dimensions and chemical composition of different types of smokeless powders, and they also keep samples and/or information about the physical dimensions of various commercially available black powders. However, in the course of criminal investigations, both laboratories have encountered black and smokeless powder samples that they are unable to identify based on their databases and samples.
Taggants could be used to facilitate the identification of the manufacturer and product line of black or smokeless powder used in a bomb without additional record keeping on the part of manufacturers or retailers. For example, the dyed powder added to some smokeless powders allows the user to immediately identify the specific product. However, it would be necessary to establish an audit trail to trace a particular powder used in a bomb from the manufacturer to the final 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. Currently, record keeping generally ends when powder is shipped from the manufacturing facility to either distributors or retailers.
Establishing the characteristics of an ideal taggant for black and smokeless powders is the first step in assessing the practicality of real identification taggants. Ideal characteristics are by their nature unattainable, but by establishing these criteria, proposed taggant concepts may be judged against agreed-upon characteristics. The ideal taggant would have the following characteristics, which are not necessarily of equal importance: no real or perceived health or safety risks, forensic applicability and utility for law enforcement, chemical and physical compatibility with black and smokeless powders, no adverse effect on powder or ballistic performance, no adverse environmental impact or contamination, low cost to various links in the chain of commerce, no viable countermeasures, and unique information that is easy to read.
A large number of companies and other organizations proposed taggant concepts that were considered by this committee. One of these taggants has been used since 1980 in explosives in Switzerland, but many of the taggant technologies presented to the committee remain in the conceptual stage, and extensive research, development, and testing would be required to produce a viable commercial product.
Although not intended as such, some commercial smokeless powders in the United States do already incorporate a kind of taggant. These smokeless powders contain colored propellant granules that aid the reloader by providing a means for visual identification of the product. However, these dyed products also have served another purpose: bomb investigators have indicated to the committee that when the dyed powder granules are recovered at a bomb scene, they facilitate the identification of the powder used and aid the investigation.
Depending on the amount of information encoded in the taggant, the frequency with which the manufacturer changes the codes, and the extent of record keeping in the distribution system, tagging of black and smokeless powders could provide investigators with information on the manufacturer, specific product type, and chain of ownership. Taggants could also help to determine if different bombing incidents are connected, and once a suspect has been identified, taggants from a bomb scene could be matched with taggants found in the suspect's possession.
Findings and Recommendations
Information and Statistics
Finding: Bombs that use black or smokeless powder cause a relatively small number of deaths and injuries, but their potential for use in terrorist activity is important. Typically over the past 5 years, about 300 "significant"5 bombing incidents each year have involved black or smokeless powder, and these bombings caused on the order of 10 deaths, 100 injuries, and $1 million in property damage annually.6 Although the number of incidents attributable to terrorism is currently very low—in the range of one or two incidents per year—the committee notes that when bombing incidents are acts of terrorism, the target is larger than the physical location of the explosion, since a goal is to induce panic or fear among the general population.
Finding: The databases on bombing statistics as currently compiled by two federal agencies contain serious discrepancies and are not sufficiently comprehensive. To reach informed, appropriate decisions about legislation involving marking or tagging of explosives, policymakers need access to accurate and detailed information about the use and effects of improvised explosive devices in the United States. Improved data are needed so that interpretive correlations and trends in criminal activity can be readily extracted, especially for bombings judged to be "significant" according to specified criteria.
RECOMMENDED ACTION: A single, national database on bombing statistics that is comprehensive, searchable, and up-to-date should be established.
Both the ATF and the FBI are currently improving their systems for handling the reporting, updating, and storage of bombing data in ways that should make the data more accessible and searchable for analysts. Incentives designed to encourage reporting of bombing incidents by local law enforcement agencies would increase the accuracy of federal data. A single reporting form submitted to a single database would reduce delays in publishing these data.
Finding: Pipe bombs and similar explosive devices that use black and smokeless powders can be detected by exploiting both the properties of the powder itself and those of the container.
Finding: Current x-ray systems are capable of detecting explosive devices containing black and smokeless powders and are effective when placed at a portal or when used in portable equipment to examine a suspicious package. Current x-ray technologies are not suitable for quickly screening large numbers of packages or for performing large-area searches. In addition, x-ray images must be examined by trained personnel or require the use of complex pattern recognition software to determine if the contents of a package resemble an explosive device.
Finding: Both black and smokeless powders contain volatile compounds that are detectable by dogs. Canine searches are now the only viable means of conducting large-area searches for hidden explosive devices. However, the circumstances that can interfere with canine detection of powders and the exact chemicals and concentrations of chemicals that dogs are able to detect are not currently well understood.
RECOMMENDED ACTION: Further research should be conducted on canine detection of bombs made with black and smokeless powders enclosed in various containers. Research should also be conducted on the development of inexpensive and portable instrumental sensors that mimic canine detection.
Better knowledge of how dogs detect devices containing black and smokeless powders would enable more efficient and appropriate use of dogs in examining large-areas and buildings and would assist in the development of instruments capable of mimicking the methods by which dogs detect powders. Depending on their size, cost, and speed, such instruments could be used for large-area searches and for high-throughput, routine screening of packages.
Finding: Detection markers added to black and smokeless powders could assist in the detection of explosive devices in several situations: large-area searches,
examination of suspicious packages, rapid and routine screening of large numbers of packages, and enhancement of canine ability to detect black and smokeless powder bombs. A detection marker's value to law enforcement for detecting explosive devices containing black and smokeless powder would depend on the properties of the added marker, such as its degree of delectability through a sealed pipe or layers of wrapping, and on the portability and cost of the associated detection equipment, as well as its range and sensitivity.
Finding: No current marking system has been demonstrated to be technically feasible for use in black and smokeless powders. While vapor markers have been successfully introduced into plastic and sheet explosives, there has not been a definitive study of how such markers might work in black and smokeless powders. Some issues of concern include the high volatility and the toxicity of vapor markers such as DMNB.
RECOMMENDATION: Detection markers in black and smokeless powders should not be implemented at the present time.
X-ray systems and dogs currently provide a strong capability for detecting bomb containers and unmarked black and smokeless powders in the scenarios considered by the committee, and most powder bombings currently take place at locations in which deployment of bomb detection systems is not practicable (see Table 1.4 in chapter 1). Therefore, the committee believes that the effectiveness of a marking program would be limited at the present time. Institution of a marking program would incur significant costs. At the current level of fewer than 10 deaths and 100 injuries per year and very few terrorist incidents, the committee believes that the benefits are not sufficient to justify such a marking program. If the threat were to increase substantially in the future and test data were available, benefits might exceed costs, and a marking program might be warranted. A marking program for black and smokeless powders would be justified only if three criteria were met: the frequency and severity of black and smokeless powder bombs were found to be high enough to justify marking; the markers 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 social benefits of markers were found to outweigh the costs of their use.
RECOMMENDED ACTION: Research should be conducted to develop and test markers that would be technically suitable for inclusion in black and smokeless powders. The marking schemes studied should be those that would assist in large-area searches or rapid screening of a large number of packages.
More information and work are needed on marking technologies. Should it become necessary for policymakers to mandate the implementation of more in-
tensive control procedures, the agencies concerned would then have the data necessary to make informed decisions about markers.
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.7 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.
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 black and smokeless 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.8 Such an effort would also be strengthened by a formal program of coop-
eration 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 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.
Finding: Taggants added to black and smokeless powders 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.9 Although new taggant
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.
RECOMMENDATION: If the type or number of bombing incidents involving black and smokeless powders increases in a way that leads policymakers to believe that current investigatory and prosecutorial capabilities must be 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 appropri-
ate 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 are being made. The type of taggant program and/or level of record keeping could be chosen to reflect the threat that these measures are 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.