Nursing organisations last night described the case as almost unprecedented in nursing.
A spokesman for the Psychiatric Nurses Organisation said it could not condone the behaviour of any nurse who mistreated a patient and that systems were in place to ensure best practices were monitored and maintained.
"We would also like to offer our sympathy to the relatives of the patient who died," the spokesman said.
A report by the Psychiatric Nurses' Association last month revealed that psychiatric nurses experienced 47 per cent more assaults in 2005 compared to 2001.
Nurses reported being stabbed, bitten, head-butted, groped and kicked, and attacked with weapons such as fire extinguishers, a pool cue, blood-filled syringes and crutches.
Dave Hughes, the general secretary of the Irish Nurses' Organisation, said while a special committee was looking at ways to protect staff, assaults by nursing staff on patients were an "extremely rare" occurrence and had probably "almost never" occurred.
