"He was the first man I ever killed."
Accused murderer David Harold Eastman, 73, allegedly whispered this sentence alone in his Reid unit a year after Canberra's top cop had been executed.
On the same day, Mr Eastman also allegedly said: "I had to kill him sitting down".
The phrases were captured by police bugs, installed to spy on Mr Eastman, by detectives investigating Colin Winchester's 1989 assassination.
An ACT Supreme Court jury was on Tuesday told the Crown would rely on the recordings during Mr Eastman’s trial for the murder of Canberra's chief police officer.
Mr Eastman has pleaded not guilty.
Australian Federal Police Assistant Commissioner Mr Winchester was gunned down as he sat in his car after he had pulled into his neighbour's driveway about 9.15pm on January 10, 1989.
Mr Winchester was killed with two bullets to the head, shot at close range.
Prosecutor Murugan Thangaraj, SC, completed his opening address to the jury on Tuesday morning.
Mr Thangaraj said the recordings, to be used in evidence during the trial, would show that Mr Eastman would talk to himself, often in whispers, and made a number of comments relevant to the case.
The silk outlined three crucial phrases he said had been admissions of his involvement.
The phrases included Mr Eastman allegedly saying, "He was the first man I ever killed" and "I had to kill him sitting down", both uttered in June, 1990.
The crown said this was in reference to Mr Winchester's execution while sitting in his car.
The following month, Mr Eastman is alleged to have said: "I mean, about the only thing he didn't do, he didn’t provide me with a bag of stones".
Mr Thangaraj said this had been a reference to the Biblical tale of David and Goliath.
The silk, however, warned that the quality of the recordings had been tainted by background noise, such as the radio or television.
The Crown alleged Mr Eastman would utilise background noise as he had become aware of the bugs.
Mr Thangaraj pointed out of the use of the television, as Mr Eastman had previously told investigators he did not watch it.
Jurors were told they would be supplied with transcripts of the covert recordings, however, it was up to them to determine whether the transcription matched what was said on the bugs.
Mr Thangaraj, on day two of the trial, also addressed the possibility someone else had killed Mr Winchester.
He told jurors the Crown must exclude all other reasonable possibilities to prove its case.
He said the police pursued many lines of inquiry during the investigation, including Mafia involvement.
Mention of alleged Mafia involvement briefly closed the court.
Acting Justice Murray Kellam ejected members of the public and media for about five minutes as prosecutors broached the topic.
After the court reopened, Mr Thangaraj provided jurors with 21 points, including a number of coincidences, to be met if organised crime or a professional hit man carried out the assassination.
These points included that the Mafia killer had used supersonic ammunition with a gun that had a silencer fitted, left cartridges at the scene, had killed the same person Mr Eastman had threatened, and had bought a gun from the same seller on the same day the accused had withdrawn cash.
The trial continues on Wednesday.