Bayesian approach to LR assessment in case of rare type match: careful derivation and limits

Non parametric Bayesian approach to LR assessment in case of rare haplotype match

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 i…

A nonparametric Bayesian approach to the rare type match problem

The "rare type match problem" is the situation in which the suspect's DNA profile, matching the DNA profile of the crime stain, is not in the database of reference. The evaluation of this match in the light of the two competing hypotheses (the crime stain has been left by the suspect or by another person) is based on the calculation of the likelihood ratio and depends on the population proportions of the DNA profiles, that are unknown. We propose a Bayesian nonparametric method that uses a two-parameter Poisson Dirichlet distribution as a prior over the ranked population proportions, and disca…

A solution for the rare type match problem when using the DIP-STR marker system

The rare type match problem is an evaluative challenging situation in which the analysis of a DNA profile reveals the presence of (at least) one allele which is not contained in the reference database. This situation is challenging because an estimate for the frequency of occurrence of the profile in a given population needs sophisticated evaluative procedures. The rare type match problem is very common when the DIP-STR marker system, which has proven itself very useful for dealing with unbalanced DNA mixtures, is used, essentially due to the limited size of the available database. The object-…

用于稀有类型匹配问题的似然比方法比较的决策论框架

A Decision-Theoretic Framework for Comparing Likelihood Ratio Methods for the Rare Type Match Problem

针对法医稀有类型匹配问题，提出贝叶斯决策论框架，用对数评分规则量化九种似然比方法的预期成本，并通过经验验证提供方法选择指南。

Impact of model choice on LR assessment in case of rare haplotype match (frequentist approach)

The likelihood ratio (LR) measures the relative weight of forensic data regarding two hypotheses. Several levels of uncertainty arise if frequentist methods are chosen for its assessment: the assumed population model only approximates the true one and its parameters are estimated through a database. Moreover, it may be wise to discard part of data, especially that only indirectly related to the hypotheses. Different reductions define different LRs. Therefore, it is more sensible to talk about "a" LR instead of "the" LR, and the error involved in the estimation should be quantified. Two frequen…

流匹配用于贝叶斯逆问题中的快速后验采样

Flow Matching for Fast Posterior Sampling in Bayesian Inverse Problems

本文提出用条件流匹配替代MCMC进行贝叶斯逆问题后验采样，实现摊销快速推断，并给出可计算的精度估计及渐近精确的混合采样器，在数值示例中验证了效果。