In April 2015 the Irish Supreme Court held, in DPP v JC [2015] IESC 31, that the rather strict exclusionary rule relating to unconstitutionally obtained evidence which had operated in that jurisdiction for the past twenty-five years should no longer be applied. A majority of the Court held that the seminal case in which the rule was set out (People (DPP) v Kenny [1990] 2 IR 110) was erroneously decided and, accordingly, overruled that precedent and reformulated the relevant rule. While the previous rule had operated on a rationale of protectionism, the newly-stated rule is based on principles of deterrence such that evidence will not be excluded where the relevant breach of constitutional rights is inadvertent. This is a major change of approach for the Irish criminal justice system and this case note explores the background to the change, the judgments of the Supreme Court, and the potential impact of what Hardiman J (dissenting) referred to as this “revolution in principle” ([2015] IESC 31 per Hardiman J. at [134]).