FIFTY-eight people have died either in prison or garda custody during the past five years, figures from the Department of Justice have shown.

Many of those who died were victims of drug overdoses, suicides, or assaults while in custody, according to prison officers and gardaí.

Already this year, eight people have died in prison custody, including three in overcrowded Mountjoy jail in Dublin. Five inmates have also lost their lives while serving sentences. The deaths occured at Castlerea, Cloverhill, Limerick, the Midlands and Arbour Hill prisons.

The tally for the first nine months of the year compares to 11 who lost their lives in jail in 2008.

Mountjoy has by far the worst record when it comes to deaths in custody according to the figures.

A total of 15 people – either serving sentences or on remand at the jail – have died in their cells there since the beginning of 2005. The prison was the subject of a scathing report by the prisons inspector, Judge Michael Reilly, last week who said conditions there were "inhuman".

Reilly said that on the day he had visited Mountjoy, the prison, which has a capacity for 489, was home to 680 prisoners. His report also revealed that 15 prisoners were accommodated in the reception area.

The Department of Justice said: "All deaths in prison custody are the subject of a garda investigation and an inquest held in a Coroner's Court. The cause of death is determined by a jury on the basis of the information presented to the court.

"Of the total number of deaths in custody since 2005, the cause of death has been determined formally in 28 cases. Nine deaths were attributed to natural causes, nine were classified as death by misadventure, three were classified as open verdicts, three were classified as suicide, two were classified as accidental and a narrative verdict was recorded in two cases.

"There are strategies and plans in place in all institutions for the prevention of suicides. The circumstances of each death in prison custody are also examined by a multi-disciplinary group in each institution."