Evaluation of tapelifting as a collection method for touch DNA.

The use of tapelifting for collection of touch DNA from fabrics is routine in many jurisdictions. However, there is a paucity of data relating to the effectiveness of different types of tapes for tapelifting, the amount of tapelifting required to generate a useful profile, and whether or not tapelifting is more effective than swabbing from various substrates. This research investigates these questions by comparing two tapes of different adhesive strength currently used in forensic casework (Scotch Magic tape and Scenesafe FAST minitapes), for sampling from touch deposits on four different fabrics-cotton flannelette, cotton drill woven fabric, polyester/cotton plain woven fabric and polyester strapping. Touch DNA was deposited on four replicates of each substrate. Separate areas of each substrate replicate were sampled, either by taping with one of the two tapes or by wet/dry swabbing with cotton swabs. Tape was applied over the defined sampling area once or repeatedly for various numbers of applications. DNA was extracted, quantified and profiled from all tape and swab samples as well as the corresponding sampled substrates. Significantly more DNA was extracted, and a higher proportion of alleles detected, from Scenesafe FAST tape than from Scotch Magic tape. The amount of DNA and number of donor alleles detected generally increased as the tape was reapplied to the surface, although a threshold of collection was seen for both types of tape. For two out of four substrates, taping with Scenesafe FAST collected more DNA than swabbing and, for three substrates, generated a greater median number of donor alleles. There was no significant difference in numbers of alleles between swabbing and taping from flannelette. Based on these findings, it is recommended that a tape with stronger adhesion (such as Scenesafe FAST tapelifters) is generally preferable; that more than one application of tape is suggested (however, increasing the amount of times the area is sampled can diminish collection efficiency); and that there is an advantage using tapelifting rather than swabbing for fabrics unless, such as with flannelette, there are many loose fibres easily removed during the sampling process.