Characterising degradation profiles of RNA molecules within blood stains: Pilot studies

Introduction
One of the capability gaps in a forensic investigation is the estimation or determination of the age of the stain. For example, was the blood stain deposited today or two months ago; was the semen stain deposited yesterday or five days ago, and was the balaclava worn by the suspect at the time of the robbery? A number of strategies have been proposed, one of which is the characterisation of RNA molecules as they degrade over time. Preliminary work targeting housekeeping genes have demonstrated a proof of principle [1]. Other strategies have included chemical options, for example Raman spectroscopy [2, 3]; however, to maximise the usefulness of the data, a genetic strategy would be preferred – in order that closer links with DNA profiles can be made. Consequently, characterising the pattern of RNA expression over time since deposition should produce some insights in the degradation profile. Such insights may lead to being able to offer an opinion as to the age of the stain in criminal case work. Different time scales were explored, including a 2 year study (collection at 2 year and 10 months), a 22 days study (with a collection everyday) and a 12 hour study (with a collection every hour). The data was brought together from three different studies.