This is the Final Summary Overview of the findings and methodology for a research project with the goal of producing an additional 1,500-substrata pyrolysis records for the Substrate Database (SD).
The SD assists fire debris analysts in casework, provides an extensive comparative cross-tabulation of pyrolysis/combustion products to ignitable liquid components, and affords a more comprehensive understanding of the parameters that affect statistical classification models. The current project had the following four goals: 1) development of a set of three standard burning methods that produce pyrolysis/combustion products; 2) an increase in the number of records in the SD by preparing 10 records for 150 new substrate materials; 3) a cross-tabulation of the frequency of occurrence based on identified compounds in ignitable liquids and pyrolysis/combustion products of substrate materials and a Naïve Bayes classification for the presence of ignitable liquid residue; and 4) the development of better fire debris models to incorporate into statistical methods that enable analysts to assess objectively the evidentiary value of fire-debris samples from casework. The project design and methods are described in this report. The report of project findings focuses on substrate database modifications, compound identification and frequency of occurrence for major peaks, compound identification-frequency of occurrence-Naïve Bayes classification, and the evidential value of fire debris data. The report on the latter finding addresses model effects on likelihood ratios. This report concludes that the expansion of the SD is having a direct impact on fire-debris casework in the United States and internationally by providing additional samples of pyrolysis products that were generated under different burn conditions. 1 figure and 3 cited works