A report of the 2002-2008 paternity testing workshops of the English speaking working group of the International Society for Forensic Genetics.

The English Speaking Working Group (ESWG) of the International Society for Forensic Genetics (ISFG) offers an annual Paternity Testing Workshop open to all members of the group. Blood samples, a questionnaire and a paper challenge are sent to the participants. Here, we present the results of the 2002-2008 Paternity Testing Workshops with the objective to evaluate the uniformity of DNA-profiling and conclusions of the participating laboratories as well as to clarify tendencies in typing strategies and biostatistical evaluations of the laboratories. The numbers of participating laboratories increased from 46 in 2002 to 68 in 2008. The results showed an increasing degree of concordance concerning methods and DNA systems used and a high degree of uniformity in typing results with discrepancies in 0.1 and 0.3 % of all submitted PCR-based results. The paper challenges showed uniformity in the calculation of the weight of evidence for simple cases with straight-forward genetic constellations. However, a high degree of variation existed in complex scenarios with rare genetic constellations such as genetic inconsistencies/possible silent alleles, rare alleles and haplotypes.