Reference Material for Comparison of Different Adhesive Tapes for Forensic DNA Sampling

Tape-lifting is an efficient method for collecting traces of cellular material from fabrics. Since 2006, an in-house adhesive tape has been used in casework at the Swedish National Forensic Centre, Linköping. Although this tape gives good DNA yields, we aim to replace it with a commercial tape to save cost and labour. In order to enable a fair comparison between different adhesive tapes, we have developed and evaluated a method for production of relevant reference material. One person, known to be a good shedder, wore identical long-sleeved T-shirts under controlled circumstances, and trace recovery was systematically performed with the in-house tape (3 T-shirts, total of 24 samples). Each sample was DNA extracted and quantified to find the normal variation within the reference material. The DNA recovery differed considerably between samples, with DNA concentrations between 0.010–0.48ng/μL (mean: 0.083, SD: 0.12ng/μL). Applying such a reference material for comparison between two commercial tapes and our in-house tape resulted in mean DNA recoveries plus/minus one standard deviation of 0.013±0.006ng/μL (Scenesafe FAST Box), 0.012±0.007ng/μL (Touch tape), and 0.023±0.013ng/μL (in-house tape). The in-house tape gave statistically significant higher yield compared to Touch tape (p<0.05), but for Scenesafe FAST Box the difference was not significant. The shedding of cells to clothes cannot be fully controlled. Having a systematically prepared, casework-like reference material with known variation is therefore vital for comparative studies of tapes.