A total of 173 prisoners died while serving sentences across the island of Ireland during the last decade.
There were 129 deaths in the Republic where nearly one-third of inmates died while finishing their sentences in the community on temporary release.
Northern Ireland prisons recorded 44 deaths.
The data from January 2007 to December 2016 was obtained by Belfast-based news website the Detail. Among their findings in the Republic were:
- A spike in deaths in custody in 2015, when 22 prisoners died;
- Data from the Inspector of Prisons showed that of the 76 prisoners who died since 2012, 22 were suspected suicides, 19 were drug-related, five were homicides and 28 were due to natural causes;
- One death was caused by a road traffic collision and another inmate died in a house fire while on temporary release. The Irish Prison Service refused to reveal information on the causes of deaths before then;
- Of the 62 deaths that were the subject of reports published by the Inspector of Prisons since 2012, 63 per cent (39) were of prisoners under 40. Sixteen were in their 20s, while 23 were in their 30s. Seven inmates who died were in their 40s, eight were in their 50s and five in their 60s. Two of the deceased were in their 70s, while one man was 82 when he died;
- A third  of the inmates who died were finishing their sentences in the community at the time.
In Northern Ireland:
- Maghaberry Prison saw the highest number of prisoner deaths (32) across the decade;
- A total of 18 deaths were from natural causes and terminal illness, while 17 prisoners died by hanging and six of the deaths were drug-related. The Northern Ireland Prison Service refused to reveal how many of the prisoners who died in the North were on temporary release at the time;
- In addition to the 44 inmates who died in Northern Ireland prisons, a further 13 people died within two weeks of being released from jail since 2010.
The Republic's Inspector of Prisons from 2008 until recently was Judge Michael Reilly. He oversaw major reforms of the oversight of the prison system, but died suddenly on November 26th.
In an interview with the Detail recorded days earlier, which his family has agreed should be published, he said: "Prisoners only forfeit their right to freedom.
“They don’t forfeit all of the rest of the rights members of society have – these rights are human rights which have been guaranteed by the international community.
“It’s very difficult to be dogmatic on how you can reduce deaths in custody, but obviously prison managers and personnel in prisons must be vigilant and there must be a sharing of information in prisons about vulnerable people.”
Inquests are still pending in relation to 26 prisoners who died in the Republic. The law currently requires a coroner’s investigation of sudden deaths, although new legislation making it obligatory for a coroner to examine all prison deaths has been on the drawing board for nine years.
A spokesman for the Irish Prison Service said every death in custody was a tragedy. “It should be borne in mind that deaths in custody can occur for a number of reasons including age or underlying medical issues on committal leading to death by natural causes, deaths by drugs overdose, or deaths by suicide.
“It is a sad fact that the prison population includes a significant number of individuals who are highly vulnerable.”
The families of 18 prisoners who died in Northern Ireland over the past 10 years are still waiting for an inquest to be held, despite obligations under UK law relating to prison deaths.
Queen's University Belfast academic Prof Phil Scraton sat on a panel which investigated the Hillsborough football disaster of 1989. He has called for a similar independent inquiry into Northern Ireland's prison system.
“What has been happening in prisons in Northern Ireland, particularly around the issue of vulnerable prisoners and the rate of self-harm and suicide, is of that magnitude,” said Prof Scraton.