Glass Analysis in a Metal Halide Lamp Warehouse Fire Investigation

A critical component of the scientific method used in fire investigations is the consideration of all feasible alternative hypotheses so as to not fall victim to expectation bias, where premature conclusions are reached without properly examining all relevant data. In this warehouse fire case study, investigators quickly concluded that a metal halide lamp ruptured and caused hot fragments to fall and ignite combustible materials. The lighting fixture, the fractured arc tube, and numerous lamp fragments were found in the area of origin, including a fragment with the accused manufacturer’s logo—and there were no other viable ignition sources in the area of origin. On its face, this seemed to be a reasonable hypothesis. However, there remained multiple unanswered questions about the recovered glass remnants and their connection to the accused manufacturer. Through systematic analysis of the glass, additional facts were uncovered that ultimately led to a complete dismissal of the lamp manufacturer from the case.