ZL Technologies at TREC 2009 Legal Interactive: Comparing Exclusionary and Investigative Approaches for Electronic Discovery Using the TREC Enron Corpus

Organizations responding to requests to produce electronically stored information (ESI) for litigation today often conduct information retrieval with a limited amount of data that has first been culled by custodian mailboxes, date ranges, or other factors chosen semi-arbitrarily based on legal negotiations or other exogenous factors. The culling process does not necessarily take into account the composition of the data set; and may, in fact, impede the expediency and cost-effectiveness of the eDiscovery process as ESI not initially identified may need to be collected later in the eDiscovery process. This exclusionary eDiscovery approach has been recommended by search and information retrieval technology providers in the past, in part, based on the state of technology available at the time; however, the technology now exists to perform an inclusive, content-based, investigative eDiscovery across a large document collection without the introduction of semiarbitrary exclusion factors. In this paper, we investigate whether limited document retrieval based on custodian email mailboxes results in lower recall and produces fewer responsive documents than a broader, inclusive search process that covers all potential custodians. In order to compare the two approaches, we designed an experiment with two independent teams conducting electronic discovery using the different approaches. We found that searching across the entire data set resulted in finding significantly more responsive documents and more initial custodians than implementing an approach that relies on custodian-based culling. Specifically, investigative eDiscovery found 516% more relevant documents and 1825% more initial custodians in our study. Based on these results, we believe organizations that employ an exclusionary, culling-based methodology may require subsequent collections, risk under production and sanctions during litigation, and will ultimately expend more resources in responding to eDiscovery production requests with a less comprehensive result.