One of the most notorious murderers in South Australia has died, the state’s premier has confirmed.

Convicted child murderer Bevan Spencer von Einem spent more than half his life in prison for the sexually motivated abduction and murder of 15-year-old Richard Kelvin — the son of former Adelaide Nine News presenter Rob Kelvin — in 1983.

SA Premier Peter Malinauskas confirmed on Saturday morning that von Einem died while serving a life sentence.

“The Department for Correctional Services has advised me of the death of Bevan Spencer von Einem,” Mr Malinauskas said in a statement.

“His death marks the end of a life defined by calculated brutality.

‘The Family’ murders that stole Adelaide’s innocence

One of South Australia’s most notorious killers, Bevan Spencer von Einem was convicted of the sexually-motivated murder of a 15-year-old boy. Warning: This story contains details some readers may find distressing.

“His crimes stand among the most horrific ever committed in South Australia, acts of deliberate cruelty that destroyed lives and inflicted trauma that will echo for generations.”

Police had linked von Einem to a group known as “The Family”, whom detectives suspect were also responsible for four similarly brutal — but unsolved — murders of young males four decades ago.

Alan Barnes, 17, Neil Muir, 25, Peter Stogneff, 14, and Mark Langley, 18, were each murdered between 1979 and 1982.

Police believe a group dubbed “The Family” is responsible for the unsolved murders of (left to right from top) Alan Barnes, Neil Muir, Mark Langley and Peter Stogneff.  (Supplied: SA Police)

The group thought to be responsible for their murders attracted its moniker after a detective described breaking up the “happy family” in a 1988 television interview.

‘Legacy of devastation’

Mr Malinauskas said von Einem had left a “legacy of devastation for victims’ families that can never be undone”.

“His death does nothing to erase the murder and torture he inflicted on innocent lives, nor does it ease the anger and grief carried by the families of his victims whose lives were shattered by his actions,” he said.

“The greatest tragedy is that they may never know the full truth because of his deliberate and selfish silence.

“Today, my thoughts are with the families of his victims. Their strength in the face of unimaginable suffering deserves our deepest respect and support.”

The premier said “most unforgivably” von Einem refused to cooperate with police despite having had every opportunity to do so.

“Instead, he chose silence, callous, deliberate silence, denying victims’ families even the faintest chance of closure. His decision to take critical information to the grave is an act of cruelty in its own right,” he said.

The 79-year-old first came to police attention in May 1972, when he took a man named Roger James — who had been thrown into the River Torrens and suffered a broken leg — to the Royal Adelaide Hospital.

He was later convicted of the murder of Richard Kelvin, who was last seen near his North Adelaide home in June 1983 after walking a friend to a nearby bus stop.

Police believe he was held at an unknown location for about five weeks before his body was found near an airstrip at Mount Crawford, in the Adelaide Hills, on July 24, 1983.

Von Einem was first interviewed four days later, on July 28, 1983, before the then-38-year-old was arrested in November the same year.

Von Einem, an accountant by trade, has remained in prison ever since.

After deliberating for more than seven hours, a jury found him guilty of the murder in October 1984, and he was sentenced the next month, when a non-parole period of 24-years was set.

The term was increased to 36 years on appeal.

Richard Kelvin, the son of former Adelaide Nine News reader Rob Kelvin, was murdered in 1983.  (Supplied: SA Police)

While serving the life sentence von Einem was charged with the murders of Alan Barnes and Mark Langley, but those charges were later withdrawn.

He remains the only person ever convicted of any of “The Family” murders.

Police believe he did not act alone when Richard Kelvin was abducted and murdered, with a $1 million reward still on offer for information which leads to a conviction.

Von Einem later became eligible to apply for parole in 2007, but the SA government changed laws to prevent offenders considered dangerous from being released.

In the same year, von Einem was moved to Port Augusta prison.

Then SA premier Mike Rann vowed von Einem should never be released.

“My view is that von Einem must never be allowed out of jail and that’s exactly why we passed this kind of legislation and we make absolutely no apologies for passing this law and we make no apologies that von Einem will be the first test case,” he said in 2008.

In 2009 von Einem was declared a dangerous offender, on the same day he was sentenced to a further three months in prison for possessing child abuse material in his cell.

He has never applied for parole.

Bevan Spencer von Einem was arrested in 1983 for the murder of Richard Kelvin. (ABC News)

After learning of von Einem’s declining health last month, SA Deputy Premier Kyam Maher said he did not think anyone would feel any remorse about the murderer’s demise.

“Quite frankly every day that person isn’t on this planet anymore is a good day,”

he said.

“I think South Australians are rightly — and have been for many many years — horrified by what that person has done.”