Consequently, a similar propensity in terms of transfer through handling can be hypothesized for both skin cells and other than skin material found on the palmar surface of the hand and fingers. In this respect, it is worth nothing that the vast majority of the mRNA profiles from the other than skin palmar samples analyzed in the present study also included skin markets. Thus, the simultaneous detection of skin and other body fluids on an object/surface, when combined with the results of DNA profiling, can aid to discriminate between secondary and primary transfer. Another interesting observation emerging from the mRNA profiling study was related to the poor results of the RNA analysis of the samples collected by means of wet swabs. In forensic investigations, the use of a wet cotton swab followed by a second dry swab, the so-called "double swab" technique, is a common method for collecting cellular material from objects. In our experiments, wet swabs appeared to be highly efficient tools to collect DNA. Nevertheless, it is well established that whereas DNA is inherently resistant to spontaneous hydrolysis, RNA is susceptible to hydrolytic breakdown even in aqueous pH-neutral solutions. Non-enzymatic hydrolysis of RNA may therefore explain the higher percentage of indeterminate mRNA profiling results obtained from wet swabs if compared to the ones obtained from dry swabs and stubs. Tape-lifting by means of stubs and the double swab method have been shown to perform equally well in securing epithelial cells from different surfaces, including skin. However, further research is required to investigate whether tape-lifting could represent a preferable sampling technique for stains that must undergo DNA/RNA co-analysis, and to test the efficiency of moistening media different from water, such as RNA stabilizing solutions and ethanol.