Making the most of DNA databases

The Combined DNA Index System (CODIS) was established by the FBI to hold genetic records with the intention of creating investigative leads. Since genetic catalogs such as this were first introduced to the criminal justice system, these databases have seen an enormous amount of growth, with CODIS for example now holding more than 10 million profiles.

The growth of these databases over the last few years has increased the chances of adventitious matches. This has lead to a greater number of false investigative leads, which has caused an increased strain on resources. In order to reduce adventitious matches, as well as enabling potential new applications of the database and international data exchange, additional loci can be included in the CODIS core loci. The task of reviewing and recommending changes to the core loci has been entrusted to the CODIS Core Working group, who were established specifically for this undertaking.

In research published in Investigative Genetics today, Budowle et al evaluate the performance of the current CODIS core loci and newly proposed additions through simplified analyses for adventitious hit rates. Dr Budowle further explains their research; ‘we were motivated to carry out this research because of the consequences that can occur with the selection of core genetic markers for forensic DNA databases. It is not a trivial issue and more thought and effort are needed than has been dedicated. Considerations include genetic typing performance, the service to be provided, and the cost to the public. We hope that our paper will motivate the decision makers for selecting an updated core set of markers for CODIS, and for that matter any other forensic DNA database, to draw on a greater breadth of scientific and statistical talent and perform more in depth analyses. We all want a high quality and high performance system that will serve the needs of protecting society’.  

The study suggests that the current core loci are not sufficient in meeting present demands, and that at least 19 autosomal loci, or the inclusion of Y chromosome STR loci would be required for CODIS to function effectively. Whilst this research does not claim to provide the solution to managing the CODIS core loci, by highlighting the different options open to improving CODIS through simple examples, it demonstrates the requirement for more comprehensive research to be conducted before recommendations can be followed.

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