Who polices the police—and what happens when the institutions responsible for accountability are also responsible for investigating themselves? Beyond the Thin Blue Line: Who Polices the Police? examines police power, prosecutorial authority, institutional protection, and the constitutional safeguards necessary to preserve public trust in American justice. Will Jenkins Sr. analyzes the structural weaknesses that arise when police departments, prosecutors, disciplinary systems, and other governmental institutions control too many stages of their own accountability processes. Rather than treating misconduct solely as an individual problem, the book examines the institutions that receive complaints, investigate allegations, preserve evidence, determine discipline, control disclosure, certify officers, and decide whether accountability moves forward. Topics include Internal Affairs, independent civilian oversight, prosecutorial accountability, police complaint and discipline databases, officer certification and decertification, body-worn cameras, digital evidence integrity, public-record redaction, police unions, qualified immunity, municipal liability, grand juries, and citizen participation. The book proposes a distributed accountability architecture in which no single agency or official controls every meaningful path to review. Its reforms include independent citizen commissions, stronger evidence-preservation safeguards, interoperable officer-history databases, mandatory pre-hire screening, independent review of disputed redactions, certification standards for oversight officials, and a Model Police Accountability and Evidence Integrity Act. Written as constitutional commentary and institutional reform, Beyond the Thin Blue Line argues that effective policing and constitutional accountability are not competing goals. Lawful policing becomes stronger when authority remains transparent, evidence remains trustworthy, misconduct cannot disappear across jurisdictional lines, and governmental power remains subject to meaningful independent review.