Method Aids in Detection of Fire Accelerants

Through the National Criminal Justice Reference Service, NIJ has made available the following final technical report (this report is the result of an NIJ-funded project but was not published by the U.S. Department of Justice): Statistical Assessment of the Probability of Correct Identification of Ignitable Liquids in Fire Debris Analysis (pdf, 121 pages)

Michael Sigman, Ph.D.; Mary Williams, M.S.; and Erin Waddell, Ph.D.

Standardized practices for the extraction of ignitable liquid residues and the analysis of the residues have been established and are published by ASTM International. ASTM E1618-11 stipulates that analysis of extracts from fire debris samples to be analyzed by gas chromatography—mass spectrometry (GC-MS). Data analysis is comprised of visual pattern matching of the total ion chromatogram, extracted ion profiling, and target compound analysis.

While ASTM E1618-11 provides reliability of the scientific evidence consisting of testing, peer review, and general acceptance under the Daubert standard, it does not provide a means of determining error rates. There is no mathematical basis, and data analysis results are not conducive to statistical methods. In addition, computational methods are often difficult to transition from academic research to operational forensic laboratories.

This research examined a mathematical model that allows for the detection of an ignitable liquid in a fire debris sample and the classification of the ignitable liquid. This project proposed to investigate the development of a method for classifying fire debris GC-MS data sets as: 1) containing or not containing an ignitable liquid, 2) classifying any ignitable liquid that may be present, and 3) estimating the statistical certainty of the answers to questions 1 and 2.

The results of this research provide the first large-scale demonstration of statistically reliable classification rates for fire debris as positive or negative for ignitable liquid residue. The authors detail how it is possible to both develop chemometric methods that provide reliable error rates for fire debris analysis and to transition these methods to operational forensic laboratories through online training.

Click here to download the report.

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