The man accused of bombing the National Crime Authority office in Adelaide vigorously proclaimed his innocence in a letter written while in prison after his original arrest in 1994, a court has heard.
But prosecutors have argued that the same letter also points to Domenic Perre seeking to blame someone else for the attack and asking a third person to give false information to police.
Details of the letter emerged on Monday during argument over its admissibility at Perre's Supreme Court trial.
The 63-year-old has pleaded not guilty to murder and attempted murder over the explosion, which killed Detective Sergeant Geoffrey Bowen and injured NCA lawyer Peter Wallis.
Justice Kevin Nicholson is presiding over the case with no jury after Perre opted to be tried by judge alone, effectively allowing details of the pre-trial argument to be published.
Defence counsel Gilbert Aitken said there was no evidence the letter was ever sent and in any case its admission was clearly prejudicial to his client.
"It is said that the mere writing of the letter gives rise, amongst other things, to a consciousness of guilt," Mr Aitken said.
"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 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.
But prosecutor Lisa Dunlop told the court that the letter showed Perre was considering asking someone to provide a false statement to police about aspects of the bombing.
She said it was evidence, along with other material, of establishing a consciousness of guilt.
Ms Dunlop said the other evidence would include details of intercepted phone calls between Perre and family members which included 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 included 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, the court was told.
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.
The NCA bombing has been one of South Australia's highest-profile cases, with a $1 million reward offered in 2008 for information leading to the conviction of the person or people responsible.
