Chemometric applications in fire debris analysis

Chemometric applications related to the analysis of ignitable liquids (ILs) and fire debris samples have evolved over the last 30 years. Most older papers focused on the use of chemometrics for classification of ILs by manufacturer, grade or into classes defined by the American Society for Testing and Material (ASTM) standard test method ASTM E1618. More recently, chemometric studies in fire debris analysis have focused on estimating the strength of the evidence in the form of a likelihood ratio (LR). The progression of chemometric methods from simple classification tasks to the calculation of LRs and statements of evidentiary value has implications across all disciplines of forensic science. Most of the data analyzed by chemometric methods in forensic fire debris analysis come from gas chromatography-mass spectrometry, although several studies have examined data from head space-mass spectrometry and other sensors. Retention time alignment is a challenge that must be addressed if chemometric methods are intended to have interlaboratory applicability. Several of the reports reviewed here rely on data representations that avoid retention time alignment issues. Attempts to apply chemometric methods to the analysis of ILs and fire debris samples has for the most part been an academic exercise and the results have not made their way into accredited forensic laboratories and established protocols. The chemometric methods are well-founded in statistical principles and they can provide a means of strengthening forensic fire debris analysis in the future. This article is categorized under: Forensic Chemistry and Trace Evidence > Fire Debris Analysis Forensic Chemistry and Trace Evidence > Trace Evidence Forensic Chemistry and Trace Evidence > Presentation and Evaluation of Forensic Science Output