Data are increasingly the lifeblood of an effective criminal justice system. Modern technology allows agencies to collect and exchange high-quality, actionable information. These data help frontline workers make informed decisions that reduce risk. And they provide managers and policymakers with vital information for the optimal allocation of resources. The fifth installment in our Justice Reinvestment Policy Brief Series, this white paper offers a short primer on criminal justice information systems, the status of efforts to build this infrastructure in Massachusetts, and key steps the Commonwealth can take to wield data as a tool to enhance public safety.