Jointly minimizing the expected costs of review for responsiveness and privilege in e-discovery

Discovery is an important aspect of the civil litigation process in the United States of America, in which all parties to a lawsuit are permitted to request relevant evidence from other parties. With the rapid growth of digital content, the emerging need for "e-discovery" has created a strong demand for techniques that can be used to review massive collections both for "responsiveness" (i.e., relevance) to the request and for "privilege" (i.e., presence of legally protected content that the party performing the review may have a right to withhold). In this process, the party performing the review may incur costs of two types, namely, annotation costs (deriving from the fact that human reviewers need to be paid for their work) and misclassification costs (deriving from the fact that failing to correctly determine the responsiveness or privilege of a document may adversely affect the interests of the parties in various ways). Relying exclusively on automatic classification would minimize annotation costs but could result in substantial misclassification costs, while relying exclusively on manual classification could generate the opposite consequences. This article proposes a risk minimization framework (called MINECORE, for "minimizing the expected costs of review") that seeks to strike an optimal balance between these two extreme stands. In MINECORE (a) the documents are first automatically classified for both responsiveness and privilege, and then (b) some of the automatically classified documents are annotated by human reviewers for responsiveness (typically by junior reviewers) and/or, in cascade, for privilege (typically by senior reviewers), with the overall goal of minimizing the expected cost (i.e., the risk) of the entire process. Risk minimization is achieved by optimizing, for both responsiveness and privilege, the choice of which documents to manually review. We present a simulation study in which classes from a standard text classification test collection (RCV1-v2) are used as surrogates for responsiveness and privilege. The results indicate that MINECORE can yield substantially lower total cost than any of a set of strong baselines.