Textile fibres in the respiratory tract part 1: A background study.

Fibre traces recovered from the respiratory tract have the potential to be informative in cases of suspected smothering. In order to interpret such findings, it is important to understand the background population of fibres in respiratory tract such that the probabilities of adventitious recovery of such fibres can be assigned. This study builds upon previous studies by first testing various recovery methods on both living participants and cadavers. Once the most suitable recovery methods were identified, background sampling of fibres was carried out on living volunteers in the nostrils (using swabs) and oral cavities (using a rinse and filter method), as well as on cadavers in the nasal cavity and trachea (using AccuTrans® mould). A population study was carried out on these fibres to understand the occurrences of each generic class and colour of fibre groups and their lengths in these regions. A deeper analysis of non-differentiated fibre groups was also carried out to assess the group sizes expected in the background population. Ultimately, the results of the population study align closely in terms of frequencies with the general background population of other surfaces. Fibre group sizes were also generally small, with the largest group being three fibres.