In the ACT Supreme Court on Wednesday, the man - whose name has been suppressed – denied he had been part of a group of alleged organised crime members - known as the Bungendore 11 - charged with a cannabis crop near the NSW township in the 1980s.

During questioning from defence barrister George Georgiou, SC, the man said he knew nothing of the group's alleged belief that it had been double-crossed by Australian Federal Police assistant commissioner Colin Winchester, who they thought had been paid off to guarantee protection over the drug crops.

Mr Winchester was shot twice in the head at close range as he parked in the driveway next to his Canberra home about 9.15pm on January 10, 1989.

David Harold Eastman, 72, is on trial for the murder in the ACT Supreme Court.

He has pleaded not guilty.

The court on Wednesday heard evidence the man had discussed a bullet, of the same calibre used to kill Mr Winchester, police had allegedly found in his home.

The man denied ever owning bullets or guns, saying he had never touched a firearm and claimed police had either planted the shell or made it up.

When asked about a conviction on his record from the 1970s for possession of a loaded gun, he said it had belonged to a passenger in his car.

The court also heard he had drug convictions, including for a role in an unrelated cannabis crop.

However, he denied involvement or any knowledge of the Bungendore plantation.

When asked if he had killed Mr Winchester, the man responded: "That's not correct at all".

"I’ve got nothing to hide."

Meanwhile, the jury has also listened to audio recordings collected by surveillance bugs planted in Mr Eastman’s home during the investigation.

The prosecution alleges the recordings captured Mr Eastman making admissions to the murder of Mr Winchester.

Jurors listened to the recordings with the use of headphones, however, to prevent audio interference, the tapes were not played out loud in court.

A British professor, who prepared transcripts of the recordings to aid jurors, was cross-examined on Wednesday about the reliability of forensic transcriptions of indistinct audio.

Professor John French said transcription requires an interpretation of the audio.

Lack of context for the audio, he said in response to one question, "makes it more difficult but it doesn’t make it impossible."

Professor French agreed it was true that priming, or the power of suggestion, could influence what someone heard on a piece of audio.

He said if a jury or group of people received a transcript of indistinct audio that was very wrong, they would recognise that.

But he agreed that if it was a rough fit they may accept the transcript.

He agreed that sometimes, once you felt you had heard something, it was difficult to unhear it.

From one portion of the tapes, the professor transcribed the words "I had to kill him sitting down".

The professor said that where he had transcribed the word "kill" for example, while that was what he believed the word was, he accepted it was possible it was another word.

In forensic science, "things are very seldom certain", he said.

The trial continues.