The Accuracy of Forensic DNA Testing

DNA testing for human identification or sourcing DNA evidence to prospective donors has advanced significantly in the past 30 years. Standard short tandem repeat (STR) technology started in 1994 in the United Kingdom with just four genetic loci (TH01, vWA, FES/FPS and F13A1) but now multiplex STR kits contain up to 27 loci with 6-dyes and incorporated Y-STR loci for maximum information. With these changes have come increased sensitivity of detection as well as improvements in software analysis programs to enable the routine interpretation of complex mixtures of up to four persons. This chapter describes step-by-step the basic forensic DNA test methods used in standard human identification and discusses the accuracy of the major methods and decision points used in this process. Factors influencing accuracy include evidence collection sterility, the evidence sampling strategy for testing, the choice of DNA extraction and quantitation methods, PCR amplification efficiency, instrument sampling for electrokinetic injection and software analysis settings. Specialty DNA methods such as mitochondrial DNA sequencing, YSTRs and SNP testing are also discussed in this chapter.