Unconfirmed accelerants: controversial evidence in fire investigations

Fire investigation is arguably one of the most difficult areas of investigation. The fire scene and available evidence has often been burnt, melted, smoke-stained, water-damaged and trampled on, but the fire investigator still has to make important distinctions between whether a fire was accidental or deliberate (arson). Modern fire investigations often rely on portable electronic detectors to identify ignitable liquid residue (ILR), or accelerant detection canines (ADCs), trained on a number of target substances. An analysis of cases from England and Wales, the United States of America (USA) and Canada demonstrates that sophisticated admissibility frameworks have not been effective in rejecting opinion testimony given by investigators and dog handlers that unconfirmed dog alerts where laboratory tests were negative provided proof of arson. This is problematic and controversial, and the authors conclude that such testimony is not compatible with modern forensic or scientific standards and should not be admitted into courts.