Authorities failed to protect murdered baby Bjay from his father, coroner says

A newborn suffered extensive injuries at the hands of his violent father but police, child protection workers and family members also failed to protect the baby, Tasmania's coroner has found.

Bjay Johnstone was just 45 days old when he died in the Royal Hobart Hospital in November 2012.

Coroner Olivia McTaggart released her damning findings on Monday, pinning the baby's death on his father Simon Adam Johnstone.

BJay's injuries were so severe there were fears if he survived, he would be unlikely to ever walk, talk, see, feed, or go to the toilet, the coroner heard.

The newborn had a fractured skull, broken pelvis, multiple broken ribs and broken legs as well as severe brain and eye damage.

The baby's grandmother Hellen Dykstra said her son was violent towards BJay's mother as well.

"She would hold BJay in front of her so that Mr Johnstone could not hit her," Ms Dykstra said in her affidavit.

The coroner said there had been a "comprehensive failure" of decision-making, action and systems from Child Protection Services, Tasmania Police and other family members, who should have protected the baby.

"This failure lies primarily with CPS, which had the opportunity and power to remove BJay from his parents at birth," the coroner said in her report.

CPS had evidence of Johnstone's violence and drug use before the baby was born.

She also said police did not take the steps necessary to ensure the boy's safety when he may have suffered a "fatal injury" despite a call from a woman in the UK about the child being at risk.

Secretary of the Tasmanian Health and Human Services Department Michael Pervan said BJay's death was "a genuine tragedy".

"It is traumatic and, for many, difficult to comprehend," he said of the baby's death.

Mr Pervan said they would need to learn from a "tragic outcome" and would strive to do better to ensure children were safe from harm and abuse.

Human Services Minister Jacquie Petrusma said the government would carefully consider all recommendations and had already started redesigning the child protection system.

Police Deputy Commissioner Scott Tilyard said the recommendations would be "carefully considered".

Johnstone pleaded guilty to wilfully ill-treating a child in 2013 and was sentenced to more than two years in jail.