Risk of dna transfer by gloves in forensic casework

In the last years, the increased sensitivity of a new generation of STR kits has contributed to a stronger focus on the issue of contamination. DNA contamination can occur by either direct or indirect transfer. Direct transfer includes contact, but also activities within the vicinity of an item that may result in the transfer of DNA from an individual without any contact (speaking or coughing). Indirect transfer of DNA is when DNA from an individual comes to be on an item via an intermediary surface. Contamination within the laboratory may occur as a result of unprotected speaking, through the presence of DNA on unused laboratory gloves, and ineffective cleaning procedures. A recent study noted the transfer of dried blood from and to cotton via tools used during examination (scissors, forceps and gloves), and indicated that these instruments pose a high contamination risk if they are not adequately cleaned. In our work, we analyzed all the gloves used in one day by four operators working in our laboratory. For every glove, we evaluated the presence of contamination DNA from the operator or from other samples. The results are presented here. In forensic caseworks, it is imperative to change gloves every time after touching items or surfaces, prior to touching the exhibit. It is desirable to wear multiple layers of gloves to avoid skin exposure during the changing of gloves.