A Dublin man found guilty of IRA membership has been jailed by the non-jury Special Criminal Court for four years and six months.

Conor Metcalfe, 28, with an address at Monastery Park, Clondalkin, was found guilty in December of membership of an unlawful organisation, styling itself the Irish Republican Army, otherwise Óglaigh na hÉireann, otherwise the IRA, on 24 November 2015.

The court had entered a not guilty plea on Metcalfe's behalf, as he had made no reply when the membership charge was put to him at the start of his trial.

The trial heard evidence that gardaí observed Metcalfe associating with convicted members of the IRA.

Closing the prosecution case last November, Anne-Marie Lawlor SC told the three-judge court that the fulcrum of the State's case was the belief evidence of Detective Chief Superintendent Anthony Howard.

Det Supt Howard, who is head of the Special Detective Unit, gave evidence that he believed Metcalfe was a member of the IRA on 24 November 2015 on the basis of material he had reviewed.

This belief evidence was supported by inferences drawn from Metcalfe's failure to answer material questions at interview after gardaí had invoked Section 2 of the Offences Against the State Act.

The section allows a court to draw inferences from a suspected person's failure or refusal to answer questions regarding alleged IRA membership.

Delivering judgment on 19 December last, Mr Justice Tony Hunt, presiding, said that the "combined weight of evidence" was sufficient to establish Metcalfe's guilt beyond a reasonable doubt.

He said the court was satisfied that the correct inference to draw from Metcalfe's failure to answer questions was that he was in fact a member of the IRA.

Passing sentence today, Mr Justice Hunt said Metcalfe's membership of an unlawful organisation was "persistent and active" as of September 2015.

Referring to Metcalfe, the judge explained that none of the facts in the case suggested the defendant was a "high level member" but he had "repeated, voluntary and intentional" association with convicted members of the IRA.

Having regard to the gravity of the offence, the judge said the maximum sentence was eight years in prison but the headline sentence in this case was five years.

The court heard that mitigating factors such as a guilty plea did not apply in Metcalfe's case and the judge indicated that the court had to enter a not guilty plea on his behalf at the outset of the trial.

However, the judge said in order to reflect "the modest nature" of the mitigating factors in Metcalfe's case, a straight discount of 10% would be applied.

Sentencing Metcalfe today, Mr Justice Hunt, who sat with Judge Sinéad Ní Chúlacháin and Judge Cormac Dunne, sentenced the father-of-four to four years and six months imprisonment, backdated to 10 December 2018 when he went into custody.