This book provides an in-depth examination of the instrument of collaboration with justice, one of the more far-reaching investigative tools in criminal cases by which promises are made to otherwise unwilling 'offender witnesses' in order to persuade them to testify in the prosecution of others. In it a comparison is made between the law and practice of the Netherlands and that of several other jurisdictions - Germany, Italy and Canada - in which provision is made for the instrument. Drawing on legal and empirical research, this book offers a unique insight into the instrument by comparing the legal frameworks in place in each country, as well as the application in practice and challenges encountered in this context. This book is intended for academics, practitioners and lawmakers in the field of criminal justice who wish to gain a deeper understanding of the instrument of collaboration with justice in all its facets.