Confirming fire as cause of death

Inhalation of soot particles during a fire can be confirmed by IR imaging with a digital camera, to aid forensic medical examiners in establishing cause of death. Despite their characteristic black appearance, it is not always easy to see particles of soot in the airways, lungs and stomach of a victim, partly because they are a similar colour to lung tissues, red blood and stomach contents. By using an IR digital camera with an IR source and a polarising filter, scientists in Japan have shown how easy it is to visualise inhaled soot.

In three test cases from real fires, the airways and stomach contents of three victims were photographed. With an ordinary digital camera, the soot was difficult to distinguish from the coloured background but the IR set up left no room for doubt. The soot appeared black against the background tissues which were lighter in colour.

By adopting the technique, it will help to clarify fire as a cause of death, especially if the photographs are submitted to a court as evidence and laypersons are expected to make judgements. It will be particularly valuable when few soot particles have been inhaled.