Exploring the Performance Impacts of Training Predictive Models with Inclusive Email Threads

Email threading is a commonly used tool by legal practitioners to streamline document review and classification in legal proceedings. Threading organizes component pieces of an email thread together to effectively reduce a dataset. The most inclusive threads and their associated document attachments are maintained, and non-inclusive or duplicative thread components are set aside. However, as data volumes continue to grow and outpace deadlines for legal proceedings, practitioners often look to incorporate multiple cost-effective and defensible technology solutions to further reduce or otherwise accelerate document review and classification. One such technology is predictive modeling – known in the legal industry as ‘predictive coding’ or ‘Technology Assisted Review (TAR)’ – which is a popular tool used to augment a manual document review and classification process. Like email threading, predictive coding has become more commonplace recently for its proven ability to minimize manual document classification, thus reducing the time and cost associated with this aspect of legal proceedings.In this study, we explore the performance impacts of layering predictive modeling onto an email threading reduction workflow. Generally, a predictive model is established first, and email threading is layered onto the scored output to further reduce and streamline document review. Our research evaluates a reversed workflow, where a population is initially reduced to its inclusive email threads, and this limited dataset is used to train and apply a predictive model to the larger population of documents for classification. Using classified data from four real-world legal proceedings, we compare the performance impact of email threading on predictive modeling by 1) training a model using all positive and negative examples, 2) training a model using positive and negative examples from only inclusive email threads, and 3) training a model using positive examples from only inclusive email threads, but negative examples from all emails. The results of our research provide thoughtful, empirical insights for legal practitioners to review when exploring the deployment of both email threading and predictive modeling into a single, cohesive document classification strategy for their legal proceedings.