A dedicated, small and secretive unit within the Gardaí run Ireland's Witness Security Programme.
It is used to counter attempts by criminal gangs and others to prevent the normal functioning of the criminal justice system - including through threats and the use of violence and intimidation of witnesses.
The programme has been thrust back into the spotlight after former Sinn Féin councillor Jonathan Dowdall may be taken into protective custody after implicating others in the Regency Hotel murder.
Michael Doyle is a news reporter with the Irish Sun.
He told Moncrieff there are only about 20 to 30 people in Ireland's WSP, including some families.
"The Witness Protection Programme - or in Ireland as it's called the Witness Security Programme - was introduced as part of the investigation into the murder of Veronica Guerin.
"The first people who entered the programme were Russell Warren, Charles Bowden and John Dunne - who were the three main State witnesses against [John] Gilligan back at this trial back in 2000.
"The three of them, as far as we're aware, are still part of that programme".
He said it is a relatively small operation.
"Over the years there's been a number of people who have come into it and then come out of it.
"But it still exists, it's a very small programme - there's a dedicated, small secretive unit within the Gardaí who look after it.
"It's been in the headlines over recent years because of the witness Joey O'Callaghan, and the popular podcast has brought it back into the spotlight".
No Government involvement
He said the programme has no legislation or oversight
"No legislation was brought in to legalise it.
"It is supported by some legislation... but there's no legal overtures as such.
"There's no Government involvement as such - they do have an annual budget of about €1.5 million to €2 million.
"They can request more if there's a particular year where more people go into it."
Where do people go?
"They send people, certainly from Ireland, to English-speaking countries.
"[The] UK, USA, Canada, Australia, South Africa - mainly because obviously that will help them settle more.
"We also have people in Ireland who are part of the witness protection programmes from other jurisdictions.
"So the Gardaí do work with law enforcement from other countries to house or home witnesses they might have".
How it works
New identities are given to people within the passport system.
"They do re-settle them abroad, but it's done within the passport system here as far as we're aware.
"They need completely new papers, a totally new identity - it's how it works obviously.
"The Gardaí here don't offer protection in a foreign jurisdiction, but they would have a number to call from local law enforcement if there was any issues they might have".
Who pays for it?
"The State houses them, as far as we know, as long as they're part of the programme.
"They are given money, because they're pretty much asked to pack in their jobs... and move abroad.
"They are encouraged to find jobs or find work if they can - but as far as we're aware the State do pay".