An improved method for STR analysis of bloodstained denim

Indigo dye is used to dye denim and other fabrics. It is now accepted that if this is co-extracted with the DNA, it may inhibit: PCR amplification. A simple, improved method is described for the extraction of DNA fi-om bloodstained denim for PCR amplification and short tandem repeat (STR) analysis. The DNA was extracted by constructing a blotting system using capillary action to draw a saline solution through the denim. The transferred material was collected onto nylon membranes and these were processed by chelex extraction. A variety of coloured denim substrates and other heavily dyed fabrics, including case work samples were used. In all cases the DNA was extracted, amplified and typed correctly.