Explosive Residues at Post-Blast Scenes
Written by Dr. Max M. Houck   

ANSER Jeff Miller military post blast evidence trace materials collectionSee this article in its original format in the Digital Edition!

BOMBINGS pose tremendous challenges to the scene investigator. Chaos and confusion predominate as investigators and law enforcement try to save lives, secure the scene, preserve evidence, and make sense of the destruction.

Additional pressures include limitations of time to access the scene, safety concerns for personnel, and jurisdictional issues. In these difficult environments, whether on the scale of a pipe bomb or an entire city block, it is often the smallest bits of evidence—down to nanograms, in some cases—that can provide the best leads and evidence to solve the crime.

Advanced chemistry techniques now allow forensic scientists to utilize microscopic traces of evidence to sort out and source explosives and their manufacturers. Collecting trace residues at a bombing scene, however, can be difficult for all the reasons mentioned above, in addition to the delicate nature of explosive residues and the chances for contamination at such messy scenes.

In recognition of these challenges, the Technical Support Working Group (TSWG) solicited provision of field, technical, and training resources for post-blast scene investigators in civilian and military bombing situations to help with collection of trace explosives materials, and awarded the project to ANSER, an operating unit of Analytic Services, Inc.

The project included three phases: The generation of (1) a field reference guide, (2) a technical reference guide, and (3) a live training event.

All materials were developed with direct input from the FBI, the ATF, military explosive ordnance experts, counter-terrorism experts, state and local bomb-squad technicians, and both operational and academic forensic laboratory trace-evidence experts. The content is unclassified material, making it useful to all scene investigators regardless of agency or clearance.

Resources for the entire forensic community

Trace Explosive Materials Field Guide ANSER TSWG

  • The Trace Explosive Materials Field Guide is a rugged, pocket-sized book-let with information that is organized and condensed for personnel at the scene. Color-coding in the margins easily indicates separate sections. The guide is designed for ease of visual reference; the text is limited to allow the reader to search quickly and find the information that is immediately needed. The target audience for this resource is the post-blast investigator with limited training. The field guide offers condensed scenarios (such as collection with limited time; collection on the battlefield; collection at a clan-destine manufacturing site; and collection from a person of interest) to provide guidelines for common scenarios.
  • The Trace Explosive Materials Reference Guide is a detailed desktop book with more than 250 pages of figures, tables, and diagrams. The guide serves as a text for reference or training. The reference will be available from TSWG electronically or in its printed format through the Government Printing Office. “The Reference Guide is not intended to replace agency policies or standard operating procedures (SOPs),” said Don Housman of ANSER, “but acts as a resource for training, standards development, and research.”
  • An interactive CD was produced by the National Forensic Science Technology Center (NFSTC) in Largo, Florida. NFSTC has a strong history of producing online and electronic learning and reference materials for the forensic community.
  • To promote discussion and offer a demonstration of the techniques listed in the guides, a live training session was held for local, state, and federal agencies at the Fairfax County (Virginia) Police Training Facility. Personnel and experts from ANSER taught the session. The techniques were demonstrated by Don Sachtleben, a former FBI explosives expert with unique professional experience that includes (among many others) the 1993 and 2001 World Trade Center bombings, the U.S. Embassy bombings in Africa, and the Unabomber case.

Fighting popular perceptions

The training began by showing the group a scene from a popular television show (CSI: Crime Scene Investigation) depicting forensic experts examining a post-blast site. The actors walk directly into the scene and immediately offer definite opinions about how the bombing occurred. The training room erupted in snorts and giggles from the experts as the actors gave specifics about exactly where the victim was standing when the bomb went off and then conducted unrealistic on-scene analyses that included lighting a material over the deceased’s body and then declaring “Gunpowder!”

Although the actors’ dialogue in this fictional scene was easily dismissed by the experts, Sachtleben reminded the attendees that these are the perceptions that have to be countered. “There is no way to walk into a scene, poke a few things, stick your finger in the air for wind direction, and say, ‘Low velocity explosive, 3- to 4,000 feet per second.’ But that’s what people think happens—and this guide helps counter those inaccurate perceptions,” said Sachtleben.

By providing more accurate methods and information for on-site processing (see photo on next page), the guide prepares investigators so they can better manage the layperson’s expectations for what can be done.

The formal training, based on the material in the reference and field guides, offered five scenarios: a best-situation scenario; a time-limited scenario; a battlefield scenario lasting 20 minutes; collecting evidence from a suspect individual; and a clandestine explosives manufacturing site. It was emphasized that there is no such thing as “unlimited time” at a crime scene. As Sachtleben noted, “They always say, ‘We’re glad you’re here… When will you be done?”’

Time limitations for an investigation can include changing weather, political influence or demands, local jurisdictional requirements, public issues (such as closing roads or using public facilities), hostile forces, or just situational issues. The field and reference guides promote the idea of adapting to the environment of the scene. All crime scenes, but bombing scenes in particular, are non-predictive.

“When we went to the first World Trade Center bombing event in February 1993,” said Sachtleben, “we suddenly found ourselves at the largest indoor blast scene we had ever worked. We had to immediately adjust our approach.”

Safety at the scene is the primary focus: Personal safety trumps evidence collection every time. In dangerous environments—particularly battlefields—safety is paramount. It is also important to remember that the current scene may not be safe; subsequent attacks, from suicide bombers for example, or timed secondary attacks (such as another bomb set to kill or harm the responding personnel) must be kept in mind. For example, when Eric Rudolph, the Centennial Park Bomber, attacked an abortion clinic, he set secondary devices to detonate at a time when emergency and forensic personnel would be working at the scene of the first explosion.

The guide notes that the scene should first be surveyed, including an aerial survey by plane, helicopter, crane, adjacent building, or whatever is available. From the ground, mostly wreckage and chaos is all that is visible. Getting a view from above the scene allows the investigator to see patterns of debris, damage, and information. Seeing the “big picture” can aid in tasking teams, assigning areas for search, and focusing the investigation. Even simple observations, such as, “The vehicle must have been facing this direction,” can be extremely helpful in the overall investigation.

Needle in a needle stack

At a post-blast scene, looking for trace explosive residues is, to re-phrase a common cliché, like looking for a needle in a needle stack. Tiny bits of debris are seemingly everywhere and even seasoned investigators can quickly become overwhelmed. Large post-blast scenes are difficult to control and almost always cannot be held long enough to collect all trace evidence materials desired. Even in a well-defined situation (a small pipe bomb at a school yard, for example), it is difficult to collect trace explosive residues in a careful and controlled fashion. Therefore, it is often advantageous to collect the materials whole, transport them to a permanent or temporary laboratory, and then sample the relevant materials under more controlled conditions.

The post-blast guides and training resources combine practical utility with technical expertise and detail. The reference materials are available from TSWG or the GPO. Training materials can be obtained through TSWG. It is hoped that these references assist the civilian and military post-blast investigator in identifying, collecting, and preserving the best evidence possible to solve bombing incidents that are directed at civilians and troops.

For More Information

The Trace Explosive Materials Field Guide, the Trace Explosive Material Reference Guide, and the interactive CD are available upon request from the Technical Support Working Group (TSWG) office. Please note that the materials are available only to law enforcement and government agencies, and each request will be handled on a case-by-case basis. To request the materials, send details to: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

About the Author

This e-mail address is being protected from spam bots, you need JavaScript enabled to view it is a Principal Analyst with the Forensic Enterprise Division in ANSER’s Joint Operations Mission Area. Analytic Services, Inc. is a not-for-profit public service institute that provides objective studies and analyses to aid decision-makers throughout the national security, homeland security, and other select public-policy communities.

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