A four-to-three majority Supreme Court decision today has introduced a new rule concerning the admissibility of evidence in criminal trials.

A decision will be made later on whether a man, in whose case the legal issue arose and who was acquitted on burglary charges after the case against him collapsed after exclusion of evidence under a 25-year-old rule, will now be retried or whether his acquittal stands.

By a four-to-three majority, the court granted an appeal by the DPP to alter a rule which had applied since the 1990 Supreme Court "DPP v Kenny" decision. That rule effectively excluded all evidence obtained in circumstances where there was a breach of a constitutional right, whether or not that breach was deliberate or due to a mistake.

The majority court introduced a new test which provides that evidence taken in "deliberate and conscious violation of constitutional rights should be excluded except in certain exceptional circumstances.

In that context, deliberate and conscious refers to "knowledge" of the unconstitutionality of the taking of the relevant evidence rather than applying to the act concerned, the majority court said.

Mr Justice Donal O'Donnell, who formed the majority view with the Chief Justice, Ms Justice Susan Denham, Mr Justice Frank Clarke and Mr Justice John MacMenamin, said the Kenny decision was "plainly wrong" and it was "long past time it was addressed".

It is part of the Supreme Court's function to adjust its prior decisions in light of developments in the law, experience and analysis, he said.

Mr Justice MacMenamin said the reputation and integrity of the system of justice should not be adversely affected by a "good faith exception" that was "properly and faithfully applied to the exclusionary rule properly and constitutionally applied".

The test set by the majority judgments was significantly higher than in other common law jurisdictions and the new rule "redressed the balance so as to encompass community interests while ensuring that "egregious breaches" of a suspect's rights and police misconduct are checked, he said.

In a dissenting judgment, Mr Justice Adrian Hardiman said the Kenny decision was essential to the maintenance of the liberties of a citizen.

He was "gravely apprehensive" the majority decision in this case overruling Kenny, "one of the monuments of Irish constitutional jurisprudence", was "a major step in the disengagement of this court from the rights-oriented jurisprudence of our predecessors".

Also dissenting, Mr Justice John Murray said the consequences of the majority court ruling was "to change the goalposts, not during the game but after the game is over, except is it not about a game or sport, it is about a criminal trial and justice which the Constitution requires shall be considered in due course of law".

If a citizen cannot rely on a rule of law as defined by the Supreme Court and applicable at their trial without the risk that a verdict shall be set aside because the law is changed by the Supreme Court after the trial, then the integrity of the judicial process is undermined, he said.

Mr Justice Liam McKechnie also dissented and said it could not be said that the Kenny decision was "plainly wrong". The protection of rights was the primary basis of the rule set in the Kenny decision and deterrence was subsumed is not that, he said. He also considered the modification of the rule, as set out by the majority court, would be "unworkable".

The DPP had sought re-examination of the Kenny decision in her appeal against a trial judge's decision to direct the acquittal of a man on burglary charges.

Section 23 of the Criminal Procedure Act permits the DPP to appeal an acquittal to the Supreme Court on a point of law on grounds including her belief the acquittal arose from a ruling which wrongly excluded "compelling evidence".

In the appeal, the DPP asked the Supreme Court to review the exclusionary rule of evidence under which the courts refuse to allow evidence be admitted if obtained in circumstances involving a breach of a defendant's constitutional right, irrespective whether that right was breached by mistake. The exclusionary rule has effectively been applied since the Kenny case.

The DPP asked the Supreme Court to find the rule was misapplied in the man's case and to make a "conclusive" decision on the applicability of the rule to future cases, the Director's counsel Brian Murray SC told the court.

The court was urged to examine whether it is appropriate to apply the rule in circumstances where there was no deliberate or conscious breach of constitutional rights.

In the case before the Supreme Court, the man, referred to as C, was acquitted as a result by direction of the trial judge on grounds gardai had effected an unlawful entry into his home under a warrant issued under Section 29.1 of the Offences Against the State Act 1939

Section 29.1 was struck down as unconstitutional by the Supreme Court in a February 2012 judgment on another case, the Damache case, on grounds the section permitted a warrant to be issued by a person who was not independent - a Garda Detective Superintendent who was participating in the investigation.

The Damache ruling was given after the gardai raided C's home but before his trial. As a result of the Damache ruling, the trial judge said she must find the entry into C's home on foot of a Section 29 warrant was unlawful.

As a result of the finding of unlawful entry, the trial judge ruled C's subsequent arrest and detention was also unlawful and therefore certain statements allegedly made by him to gardai were inadmissible in the criminal proceedings against him.

The DPP argued gardai acted reasonably in effecting an arrest under a warrant issued under Section 29 at a time when they could not reasonably have been aware of any issues relating to the validity of Section 29.

Online Editors