Since Forensic Chemistry covers a multitude of different types of evidence, our research is very varied. More information on our major research areas is detailed below.
Application of Multivariate Statistical Procedures in Fire Debris Analysis
In arson investigations, fire debris collected from the scene is typically submitted to a forensic laboratory
where the debris is analyzed to determine the presence of an ignitable liquid. The presence of such a liquid is indicative of an intentional, rather than accidental, fire. The debris is commonly analyzed using gas chromatography-mass spectrometry (GC-MS). The resulting chromatogram shows the chemical compounds present in the debris, some of which may be due to an ignitable liquid. This chromatogram can be compared to chromatograms of known ignitable liquids to determine the presence of an ignitable liquid in the debris.
Our research in this area investigates the use of multivariate statistical procedures for the comparison of chromatograms (L.J. Marshall et al., Analytical and Bioanalytical Chemistry 2009, 394, 2049; J.M. Baerncopf et al., Journal of Forensic Sciences, 2011, 56, 71; K.R. Prather et al., Forensic Science International, 2012, 222, 242). Currently, we are using procedures such as principal components analysis (PCA), hierarchical cluster analysis (HCA), soft independent modeling of class analogy (SIMCA), and linear discriminant analysis (LDA) to investigate association and classification of ignitable liquids in simulated fire debris to the corresponding known ignitable liquid. Aspects of this research were previously funded by the Midwest Forensics Resource Center and are currently funded as part of a National Institute of Justice grant.
Extraction and Analysis of Organic Impurities for MDMA Profiling
Our laboratory is also researching methods to improve profiling ecstasy tablets based on the impurities present. These impurities originate in the tablets from the synthesis of the active ingredient, which is most commonly MDMA. A profile of the impurities present can be used to link tablets from different exhibits to common production sources or clandestine laboratories. Such information could be used by law enforcement agencies to identify drug-trafficking routes and dealer-user networks.
Over the last few years, we have investigated and compared different methods to extract impurities from seized MDMA samples. These procedures included the conventional liquid-liquid extraction, along with headspace solid phase microextraction, and microwave-assisted extraction (Giebink and Waddell Smith, Journal of Forensic Sciences 2011, 56, 1483). More recently, we have investigated the effect of different GC temperature programs on the resulting impurity profiles, using PCA to assess the ability to discriminate different exhibits. Since we began this work, the research has been funded by two Forensic Sciences Foundation Lucas Grants.
Characterization and Identification of S. divinorum
The plant, Salvia divinorum, has gained substantial media attention over the last few years. While S. divinorum is not federally regulated, the plant and/or its hallucinogenic ingredient, salvinorin A, are currently regulated in 24 states in the US. Our initial research focused on developing and optimizing a procedure to extract salvinorin A from the plant. A variety of statistical procedures were then used to investigate discrimination of S. divinorum from other Salvia species (Bodnar Willard et al., Analytical and Bioanalytical Chemistry 2012, 402, 833), as well as from other plant materials adulterated with salvinorin A (Bodnar Willard et al., Analytical and Bioanalytical Chemistry 2012, 402, 843). Subsequent research investigated discrimination of S. divinorum from related species based on the volatile compounds, determined using GC-MS, and the non-volatile compounds, which were determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Our research on S. divinorum has been funded through a grant from the Midwest Forensics Resource Center.
Elemental Characterization of Gunshot Residue
Our research in the area of gunshot residue stemmed from a request by a forensic pathologist faced with an interesting case. The case involved a severely decomposed body for which cause of death was not readily apparent. The pathologist contacted us to ask if there were any chemical methods available to detect gunshot residue in severely decomposed tissue samples. Since there was no such method reported in the literature, we began to investigate possible methods, using porcine tissue as the model for method development. We focused on using inductively coupled plasma mass spectrometry (ICP-MS) to analyze the samples since this is a very sensitive technique that is used to detect elements present at very low levels. As gunshot residue contains three characteristic elements (antimony, barium, and lead), our initial research developed and optimized a procedure for the detection of these three elements in fresh and decomposed porcine tissue using ICP-MS (LaGoo et al., Journal of Forensic Sciences 2010, 55, 624). Our subsequent research investigated the potential of determining bullet type based on the elements detected in the resulting gunshot residue (Udey et al., Journal of Forensic Sciences 2011, 56, 1268).
Funding from a Forensic Sciences Foundation Lucas Grant and the American Academy of Forensic Sciences Pathology/Biology Section was used to continue this research. We are currently investigating a different analytical technique for elemental analysis: ICP-optical emission spectroscopy (OES). Although less sensitive, ICP-OES is more widely available and has lower running costs than ICP-MS and as a result, may be more accessible to a forensic science laboratory. As part of this investigation, we are using ICP-OES and ICP-MS to determine elemental differences in residue as a function of both bullet type and firing distance.
Trace Element Profiling of Document Paper
Forensic analysis of questioned documents can involve numerous types of analysis, including handwriting, ink, and paper analysis. More recently, research has focused on differentiating papers based on the elements present. These elements originate in the paper from the manufacturing and handling processes, as well as impurities in the starting materials. However, much of this research used older, less sensitive instrumental techniques, in which elements are analyzed one at a time. Such procedures are time-consuming and therefore not attractive for practical applications in forensic laboratories. Previous work in our laboratory developed an ICP-MS method for the detection of elements in document papers using ICP-MS (McGaw et al., Journal of Forensic Sciences 2009, 54, 1163 and McGaw et al., Journal of Forensic Sciences 2009, 54, 1171).However, ICP-MS may not be easily accessible to forensic laboratories due to the initial expense of the instrumentation, along with the high running costs. Similar to our gunshot residue work, we are now investigating the use of ICP-OES for the elemental analysis of a variety of different paper types produced by the same manufacturer. This involves developing a method for the analysis of the paper samples by ICP-OES and comparing to element profiles obtained for the same papers by ICP-MS. For each analytical technique, multivariate statistical procedures are used to investigate association of the same paper type, with distinction from different types, based on the elements detected. We are currently investigating whether the same association and discrimination of the paper is possible using ICP-OES, despite the lower sensitivity of this technique compared to ICP-MS.