Different studies have proved that skin contact can transfer enough DNA for successful STR typing, the success rate depends on the individual handler, which hand has been used, the activities of the individual prior to touching the object and the handled substrate. In the present study we investigate the effect of fingerprint-enhancement powder methods on subsequent STR profiling from bloodstains and latent fingerprints. The research was conducted into two phases. First we performed a study typing blood traces deposited on five different surfaces, treated with eight types of dactyloscopic powders and using three different DNA extraction methods. In the second part of our study we analyzed latent fingerprints on the same five surfaces enhanced with the eight different powders used in the first part of the study recovered with two different type of swabs (Cotton swabs and 4NGFLOQSSWABS GENETICS-COPAN).
In the first phase of the study a profile was obtained in 92% of the 120 samples analyzed, with the percentage of full profiles of 60%. In the second phase, in 55% of the 80 samples analyzed we obtained a profile, complete in 32.5% of cases, using cotton swabs. With the COPAN swabs in 76.3% of the 80 samples analyzed we obtained a profile, complete in 30% of cases.
The work has demonstrated that DNA profiling can be performed on fingerprints left on different substrates and the nature of the substrate will affect the amount of DNA that can be recovered for DNA typing analysis.