Issues in Explosives Residue Analysis A Primer for the Bar Frederic Whitehurst, Ph.D.
[Editor’s Note: This is a multi-part series deigned to educate the defense bar on important issues concerning explosive and explosive residue investigations]
Part 2: Back to the Basics: Was it the result of an explosive device in the first place? How do we know that?
Part 3: Daubert provides guidance and a means to expose limitations and evaluate explosive investigations, methods, and interpretation
Part 4: The Explosion Crime Scene: Sampling and Homogeneity Issues
Part 5: Disposition Homogeneity in explosive scene investigation
Part 6: Contamination and Cross Contamination in explosive scene investigation
Part 7: Contamination by “Render-Safe” acts of explosives
Part 8: Transportation and storage of evidence in explosive scene investigation
Part 9: Chemical analysis in explosive scene investigation
Part 10: Identifying Techniques in explosive scene investigation
Part 11: Interpretation of data in explosive scene investigation
Part 12: Experience: What makes for a proper expert in explosive scene investigation?
Part 13: Conclusion
The forensic explosives examiner is very often faced with interpreting the significance of data resulting from the analysis of residues from an explosion. Though there is usually no need to prove that an explosion occurred, the justice system often raises a need to explain an explosion. Damage at the site of an explosion may be consistent in the eyes of the layperson with the fact that a bomb was exploded when in fact the explosion or damage could have been caused by other factors such as gas or dust explosions. This leads to a requirement to reconstruct the hypothesized explosive device and to identify the explosive used in the device.
The interpretation of the data needed to answer the question, “What was the explosive used in the bomb?” is presently one of the most complex problems faced by forensic science.  Indeed, in David Fisher’s interview of Dr. William Magee, whom Fisher describes as having been the FBI Laboratory’s first chemist, Magee states that “Today, the first thing investigators search for when an airplane goes down or a bomb goes off is explosive residue.” 
When explosives initiate or explode, they have been known to leave materials which are characteristic of the original explosive. They leave products of the explosions’ chemical reactions and they often leave extremely small amounts of unreacted original explosive. The residue analyst is tasked with searching for those materials among debris and scientifically interpreting the significance of their presence and/or absence. The basis of the complexity of this science is due to the fact that explosions are chaotic, catastrophic and very fast chemical reactions, which have not been, nor will be in the near future, fully defined.
The problem is rendered even more complex by the fact that evidence of explosives residues is often not visible to the naked eye or even to a scanning electron microscope, is scattered about the crime scene in an unexplainable distribution and components of the explosive material may have been completely consumed during the explosion.
In order to address the problem one must also realize that no criminal bomb was ever initiated in exactly the same type of surroundings as any other such bomb has been or will be initiated. Bombs are used to destroy planes, houses, vehicles and a myriad of other targets of opportunity. Where the bomber is guided by politics or criminal intentions the scientist can only follow. And that following requires an understanding of the matrix in which the bomb was initiated, a matrix that is constantly changing from crime scene to crime scene.
The bar has recognized this problem, for instance, in DNA analysis where Berger  notes that “just because a test can match two samples of blood drawn in the laboratory does not mean that the test is necessarily accurate if blood is degraded or contaminated with other substances.” The problem is only made worse by the fact that the list of possible usable energetic materials found numbers in the thousands. Because of the relative ease with which explosives can be manufactured, the analyst must keep in mind the limitations of her current protocol’s ability to analyze only a select few of those materials. When the forensic examiner becomes relaxed and sure of the energetic analytes that she might see at a crime scene, the analytes used can change overnight leaving her with extensive research projects, protocol development and validation.
In comparison a forensic scientist involved with illicit drug identification may ask of the data, “Is material X present in the sample?” The analysis, which addresses that question, seeks to find one thing among many. The “war on drugs” involves essentially suppression of the extensive use of a small number of materials such as cocaine, heroin and marijuana. The scientific literature on the chemical analyses of these materials is extensive, having been driven by the illicit drug use problems throughout the world.
On the other hand, the forensic explosives analyst involved in the war against terrorism must ask the question, “What is in the sample and what is the significance of that material?” The explosives residue analyst seeks to find all that is present in the residue and to understand the significance of its presence. Where drug analysis addresses a limited number of analytes, which have been extensively studied, explosives residue analyses address a virtually unlimited number of analytes for which relatively little analysis has been conducted. The list of explosives, which have been searched for in debris, has been relatively short and protocols have been constructed to screen for the full list with minimal effort.
Excellent references concerning these analytical techniques are available and must be reviewed before a clear understanding of the extent of the explosives residue analysis problem can be appreciated. Beveridge ,  has written very comprehensive and well-documented reviews of the field. Yinon and Zitrin , have contributed to the field with excellent texts on analytical techniques. And Yinon  has discussed degradation and decomposition mechanisms of a limited number of explosives. The scientific community of experts in this field has met every three years since its first international symposium on the Analysis and Detection of Explosives at the FBI Academy at Quantico, Virginia in 1983. Each of those symposia has produced proceedings  of which the student in the field must be knowledgeable. These references and extensive study reflected in the papers of the symposia, however, help little when the bomber chooses to change the explosive material to an explosive not seen before by the forensic scientist or to put the bomb in an environment which has not been defined vis-a-vis a particular explosive and its residues. The scientist is tasked with interpreting a whole new set of data not discussed in the literature. The problem becomes even yet more complex. Generally faced with the dilemma described above a good scientist would need to take control samples of materials found at a bombing crime scene to compare with post blast residue.
After a bomb initiates however, there may be no reliable control samples. If one goes far enough from the blast scene to collect “clean” control samples, then the chance of the control actually being like the preblast material at the scene of the explosion becomes questionable. Depending on the type of explosive used one may be left only with conjecture concerning the appropriateness of the control sample. And when a new explosive material is utilized, the chemical screenings fail and the methods give data that is not understood and at worst misinterpreted.
The examiner’s customers, the field investigator and the court system, have little time to wait for scientific research. Field investigations proceed without solutions to the chemical problems. Very often cases are solved and litigation is over before the research project has reached the point of offering a hypothesis that must even then be tested. The testing of the hypothesis can be prohibitively expensive when one must test residue from candidate energetic materials in the particular matrix at a crime scene.
Imagine having to devise tests in which airplanes or buildings must be destroyed until the right “mix” of explosives is used to validate the hypothesis arrived at from the data collected from a bombing crime scene. With over two thousand bombing matters occurring in the United States in 1993 alone, the forensic casework load prohibits fast development of new methods and practically no time for validation of new protocols. There are virtually no programs in national laboratories or academic institutions directed at this problem. Funding is essentially not available until bombs explode and massive damage is done such as that in the Pan Am Flight 103 and World Trade Center matters.
 Executive Director, Forensic Justice Project, Washington, D.C., B.S. Chemistry, 1974, East Carolina University, Ph.D. in Chemistry, 1980, Duke University, J.D., 1996, Georgetown University School of Law. (202)342-6980.
 Jehuda Yinon & Shmuel Zitron, Modern Methods and Applications in Analysis of Explosives 163 (John Wiley and Sons, 1993).
 David Fisher, Hard Evidence (Simon and Shuster, 1995).
 Berger, supra note 5, at 1355.
 Alexander Beveridge, Explosives Residue Analysis In The Mid 1980’s, An Expanding And Challenging Role For The Forensic Scientist In Federal Bureau of Investigation, U.S. Department of Justice, Proceedings of The International Symposium on The Analysis And Detection of Explosives, 1983
 Alexander Beveridge, Development in the Detection and Identification of Explosive Residues, 4 Forensic Science Review 17 (1992).
 Jehuda Yinon & Shmuel Zitrin, Modern Methods And Applications In Analysis Of Explosives (John Wiley & Sons 1993).
 Jeduha Yinon & Shmuel Zitrin, The Analysis Of Explosives (Pergamon Press, 1981).
 Jehuda Yinon, Toxicity And Metabolism Of Explosives (CRC Press 1990).
 Papers from the first conference held from March 29-31,1983, are published in Proceeding of the International Symposium on the Analysis and Detection of Explosives, U.S. Department of Justice, Federal Bureau of Investigation, available from the U.S. Government printing office.
Papers from the third conference held in Mannheim-Neuostheim, Federal Republic of Germany from July 10-13, 1989, are published in Proceedings Third Symposium on Analysis and Detection of Explosives published by the Bundesakademie fur Wehrverwaltung und Wehrtechnik, Mannheim, Federal Republic of Germany,
Papers from the fourth conference held in Jerusalem, Israel from September 7-10, 1992 are published in Advances in Analysis and Detection of Explosives, published by Kluwer Academic Publishers.
The U.S. Bureau of Alcohol, Tobacco and Firearms held the fifth conference in this area in 1995 in the Washington, D.C. area however the author has not seen the proceedings as of the time of the writing of this paper.