Hand activities during robberies—Relevance to consideration of DNA transfer and detection

Abstract

It is becoming increasingly relevant to address activity level issues relating to mechanisms explaining how DNA became located at the collection site. DNA transferred to and from a surface upon contact can be influenced by the manner, frequency and relative timing of contact, plus substrate types and their histories. It is important to understand these factors during criminal activity. People touch many things during everyday activities, and in a relatively short period of time, and this may influence how DNA of a postulated source is gained or lost. Here we consider touch parameters (what, how, duration, frequency) of both hands during armed and unarmed robberies. Data were generated from the video recording of >50 events. During armed robberies, the dominant hand made ∼5 touches/min and the non-dominant hand ∼12. The majority of touches by the dominant hand was with personal items whereas the non-dominant hand mainly touched non-personal items. During unarmed robberies, the dominant hand made ∼9 touches/min and the non-dominant hand ∼12. The majority of touches for both hands was with non-personal items. These data increase our awareness of what an individual’s hand touches during a crime and importantly how that may influence the likelihood of detecting a DNA profile derived from a person of interest from items of interest. Such awareness can improve likelihood estimates of proposed scenarios.