Roger Dean was hired as a nurse at a NSW aged-care home without any reference checks two months before 14 elderly residents in a fire he deliberately lit.
Family members of the elderly victims say he should never have been hired and are now taking legal action against his employer, Quakers Hill Nursing Home, for failing to investigate his employment history and allowing him to be in charge of residents.
Dean was jailed for life over the 2011 blaze after being found guilty of 11 counts of murder.
His employment record included being investigated for workplace misconduct and being suspended from a former job because he was drug-affected at work.
In 2007 Dean resigned from St George Hospital after he was believed to have maliciously damaged a supervisor's car by screwing bolts into the tyres and throwing paint on it.
At Quakers Hill he was suspected of abusing prescription drugs and taking more than 230 tablets from the nursing home and - after learning police were poised to investigate - he set the facility on fire.
Dean used a cigarette lighter to light a fire in two beds, and during the ensuing chaos took two drug register books which he later tore up.
He initially appeared on TV talking up his efforts to evacuate residents but was subsequently charged with murder.
Nine relatives of victims launched the class action against Opal Aged Care, the owners of the Quakers Hill home, in the NSW Supreme Court.
In the statement of claim, Quakers Hill is accused of being negligent in relation to employing Dean, and also by failing to have any or any adequate, sprinkler system in place.
Dean is also being sued for negligence, over setting fire to the premises and failing to notify Quakers Hill of his history, mental health problems and drug dependence.
The court documents indicate Dean had disclosed to a former employer that he had bi-polar disorder and had been seeing a psychologist for a major depressive disorder.
Donna Austin, whose mother Alma Smith died in the blaze, said the nursing home should be held accountable.
"Putting my mum into a nursing home was one of the toughest decisions of my life," she said in a statement on Tuesday.
"It's now a decision I live to regret every single day.
"These people had a duty of care to protect my mother. They are responsible for the grief we now carry every day of our lives."
A coroner's inquest found that Dean's employer did not conduct reference checks before hiring him.
