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 bloods tained denim for PCR amplification and short tandem repeat (STR) analysis. The DNA was extracted by constructing a blotting system using capillary act ion to draw a saline solution through the denim. The transferred material w as collected onto nylon membranes and these were processed by chelex extrac tion. 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.