The Special Criminal Court is to decide later this week whether or not secret garda recordings of conversations between Gerard Hutch and the former Sinn Féin councillor Jonathan Dowdall can be admitted in evidence in a murder trial.

Gerard Hutch is objecting to surveillance that was carried out outside the borders of the State because he says it is illegal to do so.

The 59-year-old's conversation with the former Sinn Féin councillor was secretly recorded by the gardaí on 7 March 2016 after they bugged Jonathan Dowdall’s SUV.

Eight of the ten hours of their conversations were recorded in Northern Ireland, and Mr Hutch says this should not be used as evidence against him in the trial.

He has pleaded not guilty to the murder of Kinahan gangster David Byrne, who was shot dead at the Regency Hotel in Dublin on 5 February 2016.

Legal arguments concluded today.

The conversation between Dowdall (R) and Mr Hutch (L) was recorded after Mr Dowdall's SUV was bugged (file images)

Ms Justice Tara Burns confirmed that the judges had heard the audio, that both sides had said everything they wanted to say, and that everything was now before them.

She said they expect to deliver their ruling on Friday morning.

Senior counsel Brendan Grehan told the court today they were objecting to the authorisation of the surveillance device and the evidence that was harvested from it.

"We object to surveillance that was carried out outside the borders of this State," Mr Grehan told the three judges today, "if it is to be done, it must be done with legal authority, there must be a power to do this."

He said while the jeep crossed the border at 3.12pm on 7 March 2016 and the undercover officers from the National Surveillance Unit were "there waving goodbye", the gardaí knew the listening device was operating in Northern Ireland.

This was an unlawful operation of the Act in terms of the actual bug been active in Northern Ireland, Mr Grehan said, and therefore the evidence which he categorised as "the fruits of a poison tree", doesn’t become lawful just because the jeep managed to come back into the country.

Dowdall’s Toyota Landcruiser was monitored in Ardee in Co Louth at 11.36pm that night.

The Defence also says that Gerard Hutch’s constitutional right to privacy was breached.

The prosecution has already told the court that the secret garda recordings of Mr Hutch's conversations while he was in Northern Ireland were not illegal, and should be allowed in evidence because the bug was planted and removed in the Republic.

The Defence also says that Gerard Hutch's constitutional right to privacy was breached (file image)

Senior counsel Sean Gillane said the approval and authorisation for deploying the listening devices was within the State and the incontrovertible evidence was that it was deployed within the State, initiated in the State, retrieved in the State and the data recovered in the State.

"No question of extra territoriality in truth arises," he said.

The "mere happenstance" of the device crossing the border and returning could not mean what the defence has argued or such devices would be impossible to use, Mr Gillane said.

He pointed out that the Surveillance Act (2009) set out where such devices could be placed including in aircraft and ships.

"Where do airplanes go? Where do seagoing craft go?" Mr Gillane asked.

But Mr Grehan, Mr Hutch’s defence counsel said today that just because airplanes can fly anywhere doesn’t mean the Act applies everywhere.

"It must mean that it applies within the territorial waters and sky of this country," he said.

Two other men, 61-year-old Paul Murphy of Cherry Avenue in Swords, Dublin, and 51-year-old Jason Bonney of Drumnigh Wood, Portmarnock in Dublin, have pleaded not guilty to participating in or contributing to the murder of David Byrne by providing access to motor vehicles on 5 February 2016.