Effect of laundering on blunt force impact damage in fabrics

Blunt force assault is a growing issue worldwide. In New Zealand, recorded cases of grievous blunt force assault increased steadily from 1011 in 1999 to 2139 in 2008. In many cases of blunt force assault victims are struck on parts of their body covered by clothing, yet the use of damage to apparel as forensic evidence largely appears to have been overlooked. The current research investigated blunt force impact (BFI) damage in common apparel fabrics and the effects prior and post-laundering had on this damage. Two 100% cotton fabrics (single jersey knit, bull drill) were impacted as single and double layers using an impactor representative of a hammer face, the force transmitted through specimens was measured and impulse calculated. Impacting and laundering were completed cumulatively to establish the effects of impact damage on new, dimensionally stable (laundered 6 times) and aged fabrics (laundered up to 30 times), and the effects of laundering on impacted specimens. BFI left recognisable patterns of damage in specimens, although the extent of this damage varied. Laundering after the impact event altered the visible and microscopic damage. Laundering previously impacted fabrics produced holes in some specimens and some fibres exhibited failure characteristic of blunt force impact.