Progress Toward the Determination of Correct Classification Rates in Fire Debris Analysis II: Utilizing Soft Independent Modeling of Class Analogy (SIMCA)

• NCJ Number: 246001
• Journal: Journal of Forensic Sciences Volume: 59 Issue: 4 Dated: July 2014 Pages: 927-942
• Author(s): Erin E. Waddell Ph.D.; Mary R. Williams; Michael E. Sigman Ph.D.
• Date Published: July 2014
• Length: 16 pages
• Grant Number(s): 2009-DN-BX-K227
• Agencies: NIJ-Sponsored
• Publication Type: Research (Applied/Empirical)

Annotation

A multistep classification scheme was used to detect and classify ignitable liquid residues in fire debris into the classes defined by the ASTM E1618-10 standard method.

Abstract

A multistep classification scheme was used to detect and classify ignitable liquid residues in fire debris into the classes defined by the ASTM E1618-10 standard method. The total ion spectra (TIS) of the samples were classified by soft independent modeling of class analogy (SIMCA) with cross-validation and tested on fire debris. For detection of ignitable liquid residue, the true-positive rate was 94.2% for cross-validation and 79.1% for fire debris, with false-positive rates of 5.1% and 8.9%, respectively. Evaluation of SIMCA classifications for fire debris relative to a reviewer's examination led to an increase in the true-positive rate to 95.1%; however, the false-positive rate also increased to 15.0%. The correct classification rates for assigning ignitable liquid residues into ASTM E1618-10 classes were generally in the range of 80-90%, with the exception of gasoline samples, which were incorrectly classified as aromatic solvents following evaporative weathering in fire debris. Abstract published by arrangement with Wiley.