  The evaluation of a match between the DNA profile of a stain found on a crime
scene and that of a suspect (previously identified) involves the use of the
unknown parameter $p=(p_1, p_2, ...)$, (the ordered vector which represents the
proportions of the different DNA profiles in the population of potential
donors) and the names of the different DNA types. We propose a Bayesian non
parametric method which considers $P$ as a random variable distributed
according to the two-parameter Poisson Dirichlet distribution, and discard
information about names of DNA types. The ultimate goal of this model is to
evaluate DNA matches in the rare type case, that is the situation in which the
suspect's profile, matching the crime stain profile, is not one of those in the
database of reference.
