Contamination issues at crime scenes: time for a change... of clothing?
Forensic suits have been used to reduce contamination of crime scenes for decades. Previously, crime scenes were accessed by numerous individuals, each potentially contaminating the scene bringing into it unconnected trace evidence. Requirements for professionals responsible for the analysis and documentation of scenes to wear personal protective equipment (PPE) is well established. The benefits of PPE, such as crime scene suits, to reduce contamination are well known internationally. At major crime scenes, use of crime scene suits is essential and due to the serious nature of these crimes contamination of trace levels of evidence types, such as textile fibres, is imperative. Contamination-free PPE is unrealistic, but if scene personnel are unknowingly contaminating the outside of their suits prior to entering scenes can be done to reduce this problem? There are robust preventative measures available to reduce contamination which demonstrates the progress that has been made since early investigations. A basic tool in the forensic armoury is the forensic suit, also known as the SOCO suit. This hooded suit is reported by manufacturers as ideal for “protecting clothing and preventing cross contamination at the scene of crime” Whilst suits prevent contamination once in the suit, it doesn’t address issues of the wearer wearing everyday clothing, climbing into the suit at some convenient point near to the crime scene and thus potential for fibres and other trace evidence to be transferred from these clothes to the suit outer surface. Coupled with sweat and skin cells from the hands facilitating DNA contamination, the freshly-donned suit is a potential source of contamination awaiting to be shed at the scene, thereby contaminating it. A new under-suit worn beneath a forensic suit has been tested; studies including investigation of levels of textile fibre, transfer from individuals’ garments whilst donning crime scene suits. Persistence of different fibre types and tests to ascertain the comfort levels of under-suit wearers were conducted. Low, medium and high shed garments were analysed in terms of their ability to transfer fibres to the outer surface of the crime scene suit and therefore potentially contaminate any environment they subsequently come in contact with. Subsequent persistence of different fibre types on SOCO suit surfaces were identified to ascertain the potential for these fibres to be carried into crime scenes and redistributed within the scene. Contamination ‘hot-spots’ on the crime scene suits were identified. Results indicated considerable fibre contamination occurs whilst suits are being donned and its dependent on the sheddability of the garments worn underneath. Initial investigations of this new under-suit indicates that fibre contamination can be reduced dramatically (mean number of fibres were 107 and 44 for the two versions) whilst also having other benefits, such as an increase in wearer comfort and a perceived improvement in wearer temperature regulation due to wicking. Persistence of different fibres on SOCO suits indicated that fibres were retained for long enough to be taken into a crime scene and shed when undertaking common movements/activities of Scenes of Crime Officers highlighting the potential for scene contamination.