The Supreme Court has overturned a decision striking down a law under which a man was charged with withholding information in connection with the killing of a young man in Sligo.
The State and DPP had appealed against a High Court declaration that Section 9.1.b of the Offences Against the State (Amendment) Act 1998 is unconstitutional because it offends the constitutional right to remain silent and is "impermissibly vague and uncertain".
Giving the five-judge Supreme Court decision reversing that declaration, Mr Justice Peter Charleton said Section 9.1.b does not change the principle that, unless a participant wishes to speak of their own volition, the law should not compel them to self-incriminate as to their commission of a crime.
The challenge to section 9.1.b was brought by Michael Sweeney, Bog Road, Ballinrobe, Co Mayo.
He was a suspect in the Garda investigation into the killing of 23-year-old Tom Ward who was beaten to death outside his parents' home in Sligo and died on August 13, 2007.
Mr Sweeney was twice interviewed informally by gardaí before being arrested and detained for questioning in connection with the killing.
He was never charged with that offence but was charged in 2011 under Section 9.1.b with withholding information which might have led to arrest or prosecution of another person in relation to it.
He was due for trial in 2014 but that was on hold pending his challenge to Section 9.1.b.
His action was against the State and DPP and submissions were also made by the Irish Human Rights and Equality Commission.
In the Supreme Court judgment on today, Mr Justice Charleton said it was an agreed fact Mr Sweeney was warned by gardaí at all times he was not obliged to say anything unless he wished to do so.
Mr Sweeney had said "absolutely nothing", whether incriminating or exculpatory or otherwise.
He was not being prosecuted for saying anything in a police context but rather for alleged awareness of this murder and not assisting the authorities in accordance with the statutory definition.
There was "nothing" in the legislation which would enable any aspect of such interview to be used in evidence against an accused.
As a general proposition, the law also does not permit the prosecution to question an accused at trial about why they chose not to answer a particular question, he added.
Section 9.1.6 "could in no rational way" be construed as enabling a conviction merely because a person when officially questioned remained silent.
The provision, he said, applies only to those with information about the commission of a serious offence.
Those who have such information, and who know or believe that disclosing it might be of material assistance in securing the apprehension, prosecution or conviction of another person, are obliged to disclose it to the Garda.
The section specifically rules out those who have a reasonable excuse for not coming forward, he said.
That meant the requirement to co-operate applies to witnesses to crime, those who are non-participants or who otherwise lack reasonable excuse for not coming forward.
Witnessing crime or being at the scene of a crime or having information about a crime is not an offence, he said. Where a serious crime, in this case, murder, has been committed, those with relevant information are obliged by the section to communicate it to gardaí.
The inherent obligations of the section are "clear", he said. The section, as it applies to this offence, the commission by another person of murder, is not productive of inconsistent application or likely to lead to arbitrary enforcement.
The "definitional elements" of the crime are clear and do not infringe the constitutional prohibition against vagueness, he held.
Section 9.1.6 protects the right to silence of any person who does not wish to speak about their own involvement in a crime and protects the right to silence where to speak would incriminate that person, he ruled.
Orders arising from the judgment will be made next week.