Mohammed A. Tahir, Ph.D., Sandra M. Sovinski, B.S. and Gabriel E. Novick, M.D. Ph.D.
Indianapolis-Marion County Forensic Services Agency, 40 South Alabama Street, Indianapolis, Indiana 46204

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The extraction, purification and typing of DNA from densely dyed surfaces has been a challenge since the advent of DNA technology into the forensic arena. In fact, difficulty in the conventional serological analysis of such items was noted long before present DNA analysis methods were initiated. Blue jeans, carpets and car seat covers are all good examples.

We have optimized a protocol for extraction and purification of samples from these sources which consistently yields high quality DNA for both RFLP and PCR analysis. After extracting the DNA using a slightly modified FBI organic extraction protocol, samples are thoroughly washed with 8 mls of TE using a Centricon 100 filtration device. This step removes dyes and inhibitors that may potentially interfere with restriction enzyme digestion and amplification, yielding between 40 and 80 µl of sample. Subsequently, a microconcentrator Microcon 100 is used for both quantification and typing.

Four actual cases (one traffic fatality, two homicides and one sexual assault) will be presented as examples of the use and success of this strategy in actual casework.