Investigation of hair as a surface of interaction in forensic anthropology : a trap for human and environmental evidence.

When dealing with skeletal remains hair is frequently present thus becoming an important part of the anthropological analysis. With respect to bones, hair is the only tissue which may present human and environmental evidence related to the crime (similarly to skin in cases of well preserved bodies). Hence hair has a huge potential as a substratum for the search for different human and environmental traces. Given the lack of literature, the present pilot study was devised in order to verify the detectability of (a) traces related to the specific criminal event and perpetrator (blood, semen, paint, fibres) and (b) traces collected by hair during the stay of the human remains in indoor and outdoor environments. Locks of hair were set in a natural (outdoor woods), an anthropic (outdoor urban) and an indoor environment (laboratory). Apart from the negative control, samples were contaminated with sperm, blood, paint and fibres and collected at intervals up to 3 months. Two aspects were then examined: (a) the preservation of biological (blood and sperm) and abiotic traces (paint and fibres); (b) the ability to retain environmental contaminants. Each sample was macroscopically and microscopically analysed (episcopic microscope, SEM), and underwent analysis with light microscopy and luminol for semen and blood respectively. Results showed: (a) concerning the persistence of traces: biological evidence (blood and semen) was visible and detectable in the closed environment until the end of the trial while in the open environments the determination was more difficult, sperm and blood were still recognizable although severely altered after one week. Abiotical evidence (paint and fibres) remained almost unaltered regardless time and environment. (b) concerning contamination: all the environments showed mineralogical contamination specifically related to their different locations furthermore they showed, after one month, fungal hyphae. Botanical and entomological contaminants were exclusive of open environments and characterized the specific locations. A steady accumulation trend was visible only in the closed environment. Differences as regards the extrinsic contamination and the preservation of biological and abiotic evidence between samples confirm the tight link between hair and environment. Hair is an effective trap for traces while the environment is both a valuable source of traces and a strong disrupter. Despite this, in light of what has been seen in this pilot study, hair on human remains should always be analysed regardless of time of death, since traces related to the environment and/or to the criminal event or perpetrator may survive in hair.