The Dossier investigates fifteen cases of proven or alleged miscarriages of justice in south Wales between 1982 and 2016. In the first part of The Dossier Michael O'Brien presents new evidence concerning his own case, which further calls into question the actions of the police which led to his conviction. The second part of the book considers another fourteen cases for a variety of crimes including murder. These cases concern the convictions of twenty-three people, who between them have spent eighty years in prison. The earliest is Anthony Yellen, convicted of murder on a manufactured confession in 1983. The book includes the Welsh conspiracy trial, the case of the Darvell brothers in Swansea, the Cardiff Three, Jonathan Jones, the Merthyr arson case, and the Clydach murders.O'Brien calls into question methods of policing and a judicial system in which too little has changed over the past thirty years, and calls for a judicial inquiry to investigate the culture which has resulted in so many dubious and plainly wrongful convictions. No police officer has been brought to book for their part in these cases, despite the evidence produced for the convictions to be ruled unsafe. Some officers have been involved in more than one of the cases considered, and some have been promoted to senior levels in the force. Many are now retired and are no longer subject to police disciplinary procedures. How, asks O'Brien, could so many important cases have resulted in unsafe conviction, and what can be done to improve procedures in future?