As a result, the John D. and Catherine T. MacArthur Foundation decided to support a three-year multidisciplinary initiative, The Law and Neuroscience Project, that created teams (termed “research networks”) of lawyers, neuroscientists and philosophers to explore the appropriate conceptual relation of neuroscience and law and to engage in empirical investigations that would demonstrate the specific relevance of neuroscience to law. Although there was a substantial range of opinion among Project participants about the potential relevance of neuroscience to criminal law, it became apparent that a basic primer or handbook that set forth a statement of the relation as the authors understand it at present would be enormously helpful to practicing lawyers, judges, and legal policy makers as they increasingly were confronted with claims based on neuroscience information. The goal is to provide accurate information and to clarify the basic questions that will inevitable arise so that the criminal law can avoid confusion and mistakes based on inadequate understanding.