ROUND-THE-CLOCK security and medical care for one of the country's most infamous prisoners, who has been in a coma for almost a year-and-a-half, has cost the taxpayer at least €300,000.

Geoffrey Evans, who was regarded as Ireland's first serial killer, has been in a high-support unit of the Mater Hospital since December 2008.

He had suffered a massive cardiac arrest and then developed serious complications following a heart bypass operation.

Evans had been in custody at Arbour Hill Prison for 33 years and was considered unlikely ever to be released, having been refused parole countless times.

A prison officer works full-time on the job and a 24-hour watch, seven days a week, has been kept in place for more than a year.

Evans continues to be classed as a prisoner despite presenting no risk in his current state, a source said.

The source said: "There is no way around this unfortunately. Theoretically, he could come around and for that reason, he has to be guarded.

"In all likelihood, this situation will continue until his condition either improves or his health deteriorates to the point that he dies."

The 67-year-old was considered the leading force behind a chilling plan to murder one Irish woman every week in the 1970s.

Evans, along with his friend John Shaw, raped and murdered both Elizabeth Plunkett from Dublin and Mary Duffy from Mayo before they were caught.

The two men were already wanted in connection with three violent sex attacks on women in Britain, from where they originally came.

When they fled to Ireland, they decided to enact a sinister plan to stalk, kidnap and murder one woman a week.

When Shaw and Evans were eventually arrested travelling in a stolen car in Co Galway, they were questioned by the well-known former Detective Inspector Gerry O'Carroll.

Using an unorthodox interrogation technique, O'Carroll asked Shaw to kneel and pray with him for the dead women. The killer broke down and confessed.

Shaw was sentenced to life in prison for the murder of Mary Duffy and received a separate 14-year sentence for rape in February 1978.

Evans was jailed for life for the murder of Duffy and also handed down a 20-year sentence for rape.

A spokesman for the Irish Prison Service said it could not comment on security arrangements for individual prisoners.