A man convicted of deliberately lighting a blaze that ripped through a Sydney nursing home, killing 11 elderly residents, was Thursday sentenced to life in jail with no chance of parole.

Roger Dean, a nurse at the Quakers Hill Nursing Home, pleaded guilty to 11 counts of murder, telling police after the fire in 2011 that he had been "corrupted with evil thoughts".

"You won't believe it, but it was like Satan saying to me that it's the right thing to do and I try very hard to not do that," he said.

He also admitted eight counts of causing grievous bodily harm to other mostly infirm residents of the home, some of whom suffered from dementia or were blind.

Judge Megan Latham said the 37-year-old's crimes were in the worst category, calling them "heinous", "atrocious" and "greatly reprehensible" with his victims vulnerable and elderly people who were under his care.

"The pain and terror suffered by all of the victims must have been horrific," she said.

"For those who were unable to move independently and who faced the prospect of being burnt alive or suffocated by smoke, a worse fate is difficult to imagine."

Three residents perished during the inferno Dean started and eight others died later from their injuries.

The Supreme Court heard that he started the blaze at two separate points in the building as part of a "considered plan" to distract police officers and hospital management from his theft of more than 200 prescription pills.

At the time Dean was described by locals as a friendly but quiet man who kept to himself, and he was initially hailed a hero after talking to media outside the home as firefighters battled to contain the flames.

He told reporters then that he "just quickly did what I could to get everyone out".

Dean was addicted to prescription painkillers and suffered from a personality disorder, but the court was told there was no evidence he was suffering from a significant mental illness at the time.

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