A little amount of DNA is normally present in touch samples, and this amount can be further diminished during collection and processing. But because there isn't a trustworthy positive control to monitor the amount of DNA through the analytical operations, it's unclear at what point(s) the majority of the DNA is lost. We developed a set of eccrine, or fake, fingerprints in the lab using known amounts of DNA as the first step towards closing this gap. Then, using an analysis of 1200 fictitious fingerprints left on four distinct surfaces, we built a set of process controls to assess loss at critical fail points in the collection/extraction methods. We measured DNA loss at the surface, in the swab, and during extraction before using ANOVA to evaluate the results. Touch DNA samples will be used more frequently using standardised, optimised techniques as a result of improved understanding of DNA yields and the sources of loss due to focused process improvements.
