Interpreting DNA Evidence: A Review

Summary The paper provides a review of current issues relating to the use of DNA profiling in forensic science. A short historical section gives the main statistical milestones that occurred during a rapid development of DNA technology and operational uses. Greater detail is then provided for interpretation issues involving STR DNA profiles, including: – methods that take account of population substructure in DNA calculations; – parallel work carried out by the US National Research Council; – the move away from multiple independence testing in favour of experiments that demonstrate the robustness of casework procedures; – the questionable practice of source attribution ‘with reasonable scientific certainty’; – the effect on the interpretation of profiles obtained under increasingly sensitive techniques, the LCN technique in particular; – the use of DNA profiles as an intelligence tool; – the interpretation of DNA mixtures. Experience of presenting DNA evidence within UK courts is also discussed. The paper then summarises a generic interpretation framework based on the concept of likelihood ratio within a hierarchy of propositions. Finally the use of Bayesian networks to interpret DNA evidence is reviewed.