The man accused of the deadly bombing the National Crime Authority office in Adelaide told a fellow prisoner how he made the parcel explosive and that he was nearby on the day in 1994 because he wanted to watch, a court has heard.
More than 25 years after the blast, Domenic Perre is standing trial in the Supreme Court after pleading not guilty to the murder of NCA officer Detective Sergeant Geoffrey Bowen and the attempted murder of lawyer Peter Wallis.
Justice Kevin Nicholson is presiding over the case with no jury after Perre opted to be tried by judge alone, allowing details of the pre-trial argument on the admissibility of evidence to be published.
Prosecutor Sandi McDonald on Monday outlined some of the disputed material to come from a jailhouse informant who had claimed Perre had confided details in how he made the bomb and fashioned the package.
"The accused talked about Omerta and explained how it meant silence or loyalty," she said.
"The accused confided in (the informant) details of how he made the bomb.
"On (the informant's) account, the accused told him that he was nearby on the day of the bombing because he wanted to watch."
Ms McDonald told the court that during one conversation Perre also made a sign with his hands in front of his chest "to resemble a bomb exploding".
But defence counsel Gilbert Aitken said the informant's credibility would be a key issue in the trial and also pointed to Perre's vigorous assertions that he was not guilty of the crime in a letter he wrote while in custody soon after his original arrest just after the explosion.
Prosecutors argued the letter revealed a plan by the 63-year-old to blame someone else for the attack and to seek a third person to give false information to police.
They told the court the letter and other evidence gave rise to a "consciousness of guilt".
The other material included intercepted phone calls between Perre and family members during which he gave repeated directions, often in a coded way, for those people to remove, clean or destroy certain items from his home and his shed.
The directions also involved washing down items in his home and shed, such as clothes and shoes and the removal of particular tools and getting rid of the items used in the cleaning.
But Mr Aitken said there was no evidence the letter was ever sent and it was clearly prejudicial to his client.
"The letter is not an admission by Mr Perre to the conduct touching upon the events of the second of March, 1994, that being the bombing of the Adelaide office of the National Crime Authority," he said.
Mr Aitken said any determination of Perre's state of mind had to begin with the second sentence of the letter in which Perre wrote: "I am absolutely innocent, desperate and suffering in jail".
"Mr Perre is explicit in proclaiming his innocence to the charges he then faced and is explicit now in proclaiming his innocence to the charges he is facing for a second time," Mr Aitken said.
Perre was first charged over the bombing soon after the incident but the charges were dropped six months later because of a lack of evidence.
He was arrested again in 2018 following a joint investigation, lasting more than two years, by a number of state and federal authorities including the Australian Criminal Intelligence Commission.
Australian Associated Press