POPULATION-GENETICS OF STR LOCI IN CAUCASIANS

STR loci are becoming increasingly important in forensic casework. In order to be used fairly and efficiently, the population genetics of th ese loci must be investigated and the implications for forensic infere nce assessed. A key population genetics parameter is the ''coancestry coefficient'', or F-ST, which is the correlation between two genes sam pled from distinct individuals within a subpopulation. We present anal ysis of STR data, at geographic scales which range from national to re gional, rum the UK and other European sources. We implement a likeliho od-based method of estimating F-ST, which has important advantages ove r alternative methods. it allows a range of plausible values to be ass essed, rather than presenting a single point estimate, and it allows a subpopulation to be compared with a larger population from which a da tabase has been drawn, which is the relevant comparison in forensic wo rk. Our results suggest that values of F-ST appropriate to forensic ap plications in Europe are too lar ge to be ignored. With appropriate al lowance, however, it is possible to make use of STR evidence in a way which is efficient yet avoids overstatement of evidential strength.