In the last several decades, there has been an explosion in the number of amici curiae, or friend of the Court, briefs filed with the U.S. Supreme Court. Amici are not formal parties to a lawsuit, but file to help inform the Justices about the wider repercussions of the case before them. Public law scholars have long discussed whether these briefs have an impact on the Justices. This book is the first study that seeks to assess the extent of amici influence. This work examines the role of interest groups in the creation and interpretation of the right to privacy, a highly controversial right that derived almost entirely from case law. It looks at amici participation in abortion, aid in dying, family relationships, and anti-sodomy cases. This volume tracks the influence of amici arguments and data on the Justices' handling of these cases.