The interpretation of lineage markers in forensic DNA testing

Mitochondrial DNA (mtDNA) and the non-recombining portion of the Y-chromosome are inherited matrilinealy and patrilinealy, respectively, and without recombination. Collectively they are termed 'lineage markers'. Lineage markers may be used in forensic testing of an item, such as a hair from a crime scene, against a hypothesised source, or in relationship testing. An estimate of the evidential weight of a match is usually provided by a count of the occurrence in some database of the mtDNA or Y-STR haplotype under consideration. When the factual statement of a count in the database is applied to a case, issues of relevance of the database and sampling uncertainty may arise. In this paper, we re-examine the issues of sampling uncertainty, the relevance of the database, and the combination of autosomal and lineage marker evidence. We also review the recent developments by C.H. Brenner.