ASSESSING PROBABILITY OF PATERNITY AND THE PRODUCT RULE IN DNA SYSTEMS

The genetic resolution of paternity disputes begins with an intricate detection of inherited traits and finishes with a statistical inferenc e (the probability of paternity, W). Notwithstanding some initial fanf are, statistical inference is a necessary component of DNA-based pater nity tests because band patterns may be rare but not yet unique, and e ven rare events in a vacuum are meaningless. The genetic match must be combined with other evidence for relevancy, thus a Bayesian approach is preferred when computing W. This paper reviews the standard model u sed to compute W and discusses the model's various properties and assu mptions. The standard model is extended to include DNA systems in whic h alleles are operationally continuous due to measurement error. This extension avoids problems associated with 'matched/non-matched' binned decisions. After outlining the model assumptions for a single DNA sys tem, particular attention is given to the product rule - the procedure of multiplying intermediate probabilities across genetic loci to form a combined W. An empirical alternative to the product rule is also as sessed and correlated with standard procedures.