The field of forensic analytical chemistry combines the powerful laboratory methods of analytical chemistry with the acute social relevance of forensic science. My research interests in this area have broad implications for analytical derivatization, gas and liquid chromatography, mass spectrometry and multivariate statistical analysis. In turn, these projects seek fundamentally new information on the detection of explosives using instruments and/or canines. Finally, comparisons of class evidence such as hair, tape and smokeless powder will be enhanced significantly. Each of these projects is outlined below.

I. Designing Novel Laboratory Methods for the Identification of Chemical Residues on Post-Blast Debris

Protocols for the analysis of post-blast residues generally rely upon an appropriate solvent extraction, chromatographic separation and detection by a suitably sensitive and specific technique such as mass spectrometry. However, many explosives present difficulties for separation and/or detection due to low retention in liquid chromatography, thermal instability in gas chromatography, gas-phase ionization (EI or CI) that leads to uninformative and non-specific mass spectra, or easily suppressed ionization in atmospheric pressure ionization methods such as ESI and APCI. Furthermore, the use of adequate sample clean-up procedures and rigorous quantitative analysis is not common in forensic science laboratories, leading to strong interferences from sample matrixes and rapid degradation of instrument performance. Research into improved methods for black powder substitutes such as Pyrodex and Clean Shot (See Fig. 1) as well as nitrated high explosives and peroxide-based high explosives will attempt to address these needs through more creative approaches to chemical separations, derivatization techniques and conclusive identification via mass spectrometry. In addition, each research project would include validation steps using actual post-blast debris, appropriate sample clean-up, quantitative analysis of post-blast residues and subsequent estimates of yield and explosive efficiency.

Figure 1: (left to right) black powder, Pyrodex® and Clean Shot®

II. Quantitative Instrumental and Statistical Methods for the Comparison of Class Evidence

Forensic scientists often rely upon the class characteristics of a questioned item (Q) to assess whether it may share a common source with a known sample (K). In order to accomplish this, a set of discriminating analytical techniques must be available to evaluate these characteristics and assign a type to both the Q and K. If the two samples are both associated to a given type, the frequency of occurrence for the evidence type in question should be estimated and thereby the significance of the association discerned. Traditionally, class evidence has been studied qualitatively and classification of samples was achieved through visual inspection. However, the use of quantitative analytical techniques as well as computerized pattern recognition can significantly improve the reproducibility, differentiation and reliability of the data thus obtained. Particular interest areas are the comparison of electrical tape, human hair, and smokeless powder via SEM-EDS, FTIR, and GC/MS. Pattern recognition techniques such as agglomerative hierarchical clustering, principal components analysis and discriminant analysis can then be applied to this data.

Figure 2: EDS spectra of the backing from three rolls of tape. These results show an association between a questioned sample recovered from an IED (Q), a known sample recovered from a suspects’ vehicle (K) and an exemplar (Frost King brand). Both the Q and K sample were assigned to the class containing Frost King brand via Discriminant Analysis.

III. Fundamental Studies of the Volatile and Semi-volatile Compounds Emitted by Explosive Formulations

To date, the detection of hidden explosives relies upon probing suspect materials with photons or neutrons, identifying explosive residues on surfaces, or detecting volatile compounds that are emitted by the explosive formulation. Detection of these latter compounds can be achieved via instrumentation or by specially trained canines. Canine searches are thorough and result in an unambiguous, yet passive, alert to signal the presence of an explosive (see Figure 3). Currently, the speed, sensitivity and selectivity of canines cannot be duplicated by instrumentation. While instruments are designed and built to respond to particular chemical species, it is not always clear what chemical species generates a canine alert. In addition, canines have the ability to “generalize” and correctly alert to explosive formulations that are similar, but not identical, to those with which they have trained. This would tend to indicate that there are common chemical odors for some types of explosives. Research in this area will focus on quantitative characterization of the compounds in the headspace above explosive formulations, which should reflect the odor that is sampled by a canine. In turn, confirmation of these compounds in the headspace of closely-related explosives would indicate that generalization by a canine is governed by common odor compounds. It should then be possible to test the extent to which canine alerts correlate to the compounds of interest. Furthermore, the ability of canine training aids to reliably deliver appropriate odors to the canine can be evaluated, particularly in the case of the more volatile and chemically unstable species such as organic peroxide explosives.

Figure 3: Examples of a typical canine vehicle search and passive alert to the presence of explosives

Recent Publications

J. V. Goodpaster, A. B. Sturdevant, K. L. Andrews, and L. Brun-Conti "Identification and Comparison of Electrical Tapes Using Instrumental and Statistical Techniques: I. Microscopic Surface Texture and Elemental Composition" J. Forensic Sci. 2007, 52, 610-629.

J. V. Goodpaster "Household Items that Contain Explosive Compounds: A Guide for Explosive-Detecting Canine Handlers" The Detonator 2007, 34, 42-46.

P. A. Dreifuss and J. V. Goodpaster "Atmospheric Pressure Ionization LC/MS Methods for the Analysis of Black Powder Substitutes" Proceedings of the 8th International Symposium on the Analysis and Detection of Explosives, D. Garbutt, P. Pilon, P. Lightfoot, Eds., 2004, pp 168-180.

J. V. Goodpaster and R. O. Keto "Identification of Ascorbic Acid and Its Degradation Products in Black Powder Substitutes" J. Forensic Sci. 2004, 49, 523-528.

S. Ballou, J. V. Goodpaster, W. MacCrehan and D. Reeder "Forensic Analysis" Anal. Bioanal. Chem. 2003, 376, 1149-1150, J. V. Goodpaster, Guest Editor.

B. A. Benner, Jr., J. V. Goodpaster, J. A. DeGrasse, L. A. Tully and B. C. Levin "Characterization of Surface Organic Components of Human Hair by On-Line Supercritical Fluid Extraction - Gas Chromatography-Mass Spectrometry: A Feasibility Study and Comparison with Human Identification Using Mitochondrial DNA Sequences" J. Forensic Sci. 2003, 48, 554-563.

J. V. Goodpaster, B. C. Drumheller and B. A. Benner, Jr. "Evaluation of Extraction Techniques for the Forensic Analysis of Human Scalp Hair Using Gas Chromatography/Mass Spectrometry (GC/MS)" J. Forensic Sci. 2003, 48, 299-306.

J. V. Goodpaster, J. J. Bishop and B. A. Benner, Jr. "Forensic Analysis of Hair Surface Components Using Off-Line Extraction and Large Volume Injection" J. Sep. Sci. 2003, 26, 137-141.

J. V. Goodpaster, J. F. Harrison and V. L. McGuffin "Ab Initio Study of Selective Fluorescence Quenching of Polycyclic Aromatic Hydrocarbons" J. Phys. Chem. A 2002, 106, 10645-10654.

S. B. Howerton, J. V. Goodpaster and V. L. McGuffin "Characterization of Polycyclic Aromatic Hydrocarbons in Environmental Samples by Selective Fluorescence Quenching" Anal. Chim. Acta 2002, 459, 61-73.

J. V. Goodpaster, S. B. Howerton and V. L. McGuffin "Forensic Analysis of Commercial Petroleum Products Using Selective Fluorescence Quenching" J. Forensic Sci. 2001, 46, 1358-1371.

J. V. Goodpaster and V. L. McGuffin "Separation of Nitramine and Nitroaromatic Explosives by Capillary Liquid Chromatography" J. Liq. Chromatogr. Relat. Technol. 2001, 24, 1965-1978.

J. V. Goodpaster and V. L. McGuffin "Fluorescence Quenching as a Novel Indirect Detection Method for Nitrated Explosives" Anal. Chem. 2001, 73, 2004-2011.

J. V. Goodpaster and V. L. McGuffin "Selective Fluorescence Quenching of Polycyclic Aromatic Compounds by Aliphatic Amines" Anal. Chem. 2000, 72, 1072-1077.

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