Domenic Perre was transferred from the infirmity in Yatala Prison to the Royal Adelaide Hospital in mid-April, and suffered a suspected heart attack overnight.
The 65-year-old was last year given a mandatory life sentence over the bombing.
Detective Geoffrey Bowen was killed when a parcel bomb built and sent by Perre exploded in his CBD office March 2, 1994.
Lawyer Peter Wallis, who died in 2018, was also injured in the blast, losing an eye and sustaining severe burns.
Justice Kevin Nicholson confirmed the 65-year-old’s mandatory sentence in the South Australian Supreme Court for murder and attempted murder in October 2022.
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Perre was already behind bars for drug offences, so Nicholson extended his existing non-parole period by 30 years and seven months.
Prosecutors had argued the bombing was a personal attack on Bowen, due to his investigations into the family’s drug business.
“Mr Perre wanted to kill Mr Bowen but intended the NCA bomb to do its work and kill whomever it did,” the judge said.
Perre had been charged with murder shortly after the bombing in 1994, however these charges were dropped due to insufficient evidence.
He was re-arrested in 2018 after a two-year joint investigation, by a number of state and federal authorities including the Australian Criminal Intelligence Commission.
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