The influence of substrate on DNA transfer and extraction efficiency

Abstract The circumstances surrounding deposition of DNA profiles are increasingly becoming an issue in court proceedings, especially whether or not the deposit was made by primary transfer. In order to improve the currently problematic evaluation of transfer scenarios in court proceedings, we examined the influence a variety of nine substrate types (six varieties of fabric, plywood, tarpaulin, and plastic sheets) has on DNA transfer involving blood. DNA transfer percentages were significantly higher ( p  = 0.03) when the primary substrate was of non-porous material (such as tarpaulin, plastic or, to a lesser degree, wood) and the secondary substrate porous (such as fabrics). These findings on transfer percentages confirm the results of previous studies. Fabric composition was also shown to have a significant ( p  = 0.03) effect on DNA transfer; when experiments were performed with friction from a variety of fabrics to a specific weave of cotton, transfer percentages ranged from 4% (flannelette) to 94% (acetate). The propensity for the same nine substrates to impact upon the efficiency of DNA extraction procedures was also examined. Significant ( p  = 0.03) differences were found among the extraction efficiencies from different materials. When 15 μL of blood was deposited on each of the substrates, the lowest quantity of DNA was extracted from plastic (20 ng) and the highest quantities extracted from calico and flannelette (650 ng). Significant ( p p