Judicial oversight of policing: Investigations, evidence and the exclusionary rule

Police procedures and practices in the investigation of crime are shaped by many things. One particularly important constituent part of the development of investigative procedures and practices is the approach of the courts to the admissibility at trial of evidence obtained in a certain manner. While a judge can only address the specifics of whatever cases are brought before him, the judiciary as a whole have a significant role to play in terms of police accountability and governance through their development and application of any exclusionary rules of criminal evidence. This article examines the judicial oversight of policing by way of the exclusion of improperly obtained evidence at trial. Its central focus is on the development and operation of the exclusionary rule in Ireland, though relevant law in other jurisdictions, including England and Wales, the United States, Canada and New Zealand, is also considered. Particular attention is paid to the recent Irish Supreme Court decision of DPP v Cash, and its ramifications for judicial oversight of policing.