Detection of DNA within fingermarks

DNA is deposited onto a surface by touch yet few means have been developed for its in situ detection. A range of dyes are available that bind to DNA at high specificity and here we report on the use of two of these dyes to detect latent DNA. SYBR^® Green I and GelGreen were used to detect DNA within fingermarks after fingers and thumbs were pressed onto a range of substrates such as Parafilm^®. A solution of dye was then pipetted onto the mark and allowed to dry briefly. There was a high level of fluorescence where the fingermark was present indicating the dye had bound to DNA however a low level of fluorescence was present in the negative controls. To determine whether this background fluorescence was due to bacteria present on the substrates the dyes were pipetted onto a bacterial culture and the level of fluorescence was observed. It was found that SYBR^® Green I had a higher level of fluorescence compared with GelGreen™ and that both dyes fluoresce when in the presence of bacterial cells. By altering the volume and concentration of dye, ridge detail within the fingermark may be observed allowing for the possibility of not only detecting latent DNA but also using this method for human identification and fingermark comparison.