Using an interaction timeline to investigate factors related to shedder status.

A major factor that influences DNA transfer is the propensity of individuals to 'shed' DNA, commonly referred to as their 'shedder status'. In this work we provide a novel method to analyse and interrogate DNA transfer data from a largely uncontrolled study that tracks the movements and actions of a group of individuals over the course of an hour. By setting up a model that provides a simplistic description of the world, parameters within the model that represent properties of interest can be iteratively refined until the model can sufficiently describe a set of final DNA observations. Because the model describing reality can be constructed and parametrised in any desired configuration, aspects that may be difficult to traditionally test together can be investigated. To that end, we use a 60-min timeline of activity between four individuals and use DNA profiling results from objects taken at the conclusion of the hour to investigate factors that may affect shedder status. We simultaneously consider factors of: the amount of DNA transferred per contact, the rate of self-DNA regeneration, the capacity of hands to hold DNA, and the rate of non-self-DNA removal, all of which may ultimately contribute to someone's shedder status.