The Supreme Court has ruled the exclusion of evidence obtained in breach of constitutional rights should also apply to cases concerning property seized by the Criminal Assets Bureau.
In a significant decision, the court overturned previous decisions of a lower court which said the exclusionary rule did not apply to cases under the Proceeds of Crime Act.
The judgment was given in an appeal concerning a dispute over ownership of just under €20,000 seized by CAB.
The High Court must now reconsider a dispute between CAB and Michael Murphy Senior, from Riverview Estate, Cork, and his son Michael Murphy Junior, over whether CAB is entitled to orders for forfeiture of the cash.
The money was seized from the home of a girlfriend of Mr Murphy Junior at Clonard Avenue, Granagh, Co Cork, a property which the High Court also treated as his dwelling.
The seizure was made in a follow up search after Mr Murphy Junior was stopped by gardaí in May 2009 driving an Audi car with six firearms in the boot, for which he later received a six-year sentence.
The seized cash - £6,625 Sterling and €9,000 - was made subject of freezing orders after the High Court found it represented the proceeds of crime.
In the judgment, Ms Justice Iseult O'Malley set out a detailed response and legal test to be adopted by a court when a breach of constitutional rights is involved in the seizure of assets under the Act.
CAB must prove, on the balance of probabilities, the asset was not seized in unconstitutional circumstances or, if it was, it was still appropriate to make the orders sought.
If a CAB application is refused, that does not necessarily mean seized property such as firearms or drugs will be returned to the person from whom it was taken as there is no legal or constitutional right to possession of such items, she stressed.
Mr Murphy Junior, who has 43 previous convictions, was alleged by CAB to be involved in drug dealing.
His father, who lost his sight in an accident in 1983, has 21 previous convictions and CAB claimed he had a shared involvement in crime with his son, including handling stolen property.
The son claimed his money came from legitimate sources including his waste business, while his father claimed he got funds from his late mother and from begging in an effort to raise money for an eye operation.
Both men said the seized cash belonged to them and argued it was unconstitutionally or illegally obtained under an invalid warrant used to search the Clonard Avenue property.
In the court's judgment, Ms Justice O'Malley said the cash was seized from the dwelling of Mr Murphy Junior on foot of an invalid search warrant because that was issued in 2011 under Section 29 of the Offences Against the State Act, later struck down by the Supreme Court in 2012 as unconstitutional.
The "broader purpose" of the exclusionary rule is to protect important constitutional rights and values whose common themes include the integrity of the administration of justice, the need to encourage agents of the State to comply with the law, or deter them from breaking it, and the constitutional obligation to protect and vindicate the rights of individuals.
There is nothing about proceedings under the Proceeds of Crime Act that renders those underlying principles inapplicable in this case, the judge said.