Information extraction from case law and retrieval of prior cases Original Research Article

We describe an information extraction and retrieval system, called History Assistant, which extracts rulings from court opinions and retrieves relevant prior cases from a citator database. The technology employed is similar to that adopted in the Message Understanding Conferences, but attempts a fuller parse in order to distinguish current rulings from previous rulings reported in a case. In addition, we employ a combination of information retrieval and machine learning techniques to link each new case to related documents that it may impact. We present experimental results, in terms of precision and recall, for all tasks performed by the extraction and linking programs. Part of the finished system has been deemed worthy of further development into a computer-assisted database update tool to help editors assimilate historical relationships between cases into a concordance of court decisions, called a citator.