A recording made by an ambulance officer at the scene where a young mother was accidentally shot while smoking ice with friends was never heard by the jury in her manslaughter case.

Key points: Jovan Jojic was acquitted of manslaughter of Sarah Johnson-Portelli

Jovan Jojic was acquitted of manslaughter of Sarah Johnson-Portelli Audio recording from paramedic on scene was not heard by jury

Audio recording from paramedic on scene was not heard by jury Lead detective shocked by recording's exclusion from case, questions number of decisions made in trial

Young mother Sarah Johnson-Portelli, 20, died in April 2013 at a house in St Albans, in Melbourne's west.

But the man accused of her manslaughter, Jovan Jojic, was acquitted last December.

It was ruled that an audio recording made by a paramedic at the scene could not be heard by the jury because it had little probative value and would delay a trial that had already been interrupted several times for legal reasons.

But the decision to leave the recording out of the evidence has left the lead detective in the case shocked.

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"I [was] astonished, absolutely astonished," former homicide detective Allan Birch told 7.30.

"We're dealing with a young lady's death from gunshot wounds, we're dealing with the liberty of an accused person.

"I mean, no more serious crime can a person commit than taking another person's life.

"There were a number of decisions made in the conduct of this trial that, even with my experience, I just couldn't fathom — it just seemed a long way from fairness."

Sarah Johnson-Portelli was shot in the head in the early hours of April 7, 2013. ( Supplied )

In the recording, one of only two witnesses to the shooting, Phil Spadaro, is in great distress at the death of Ms Johnson-Portelli.

Mr Spadaro was also accidentally shot in the leg that night.

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Homicide detectives believe the recording throws doubt on the defence argument in the case that the two witnesses to the shooting — Mr Spadaro and Emilija Dilber — colluded to implicate Mr Jojic.

"[At] that time of the trial, the credibility of Phil Spadaro has been heavily attacked by the defence — that he had concocted a story, he had collaborated with … Emilija Dilber, to come up with this account that Jovan [Jojic] fired the fatal shot," Mr Birch said.

"This [recording] said well hold on, here's the first emergency service person on the scene, recording and his account is the same as hers — where was the collaboration? Where was the conspiracy?"

The ambulance paramedic has confirmed to 7.30 that she never saw Ms Dilber.

Paramedic was not included in the trial

Partway through the trial, when the detectives discovered the recording buried on their computer system, paramedic Cassie was on a cruise ship.

She exchanged 20 emails with detectives and offered to give evidence by video link to clarify what was being said in the audio recording when she docked at the next port several days later, but the judge in the case, in the absence of the jury, refused the crown's application.

Cassie, who fears for her safety like many other witnesses attached to this case, has not spoken out about the incident and did not want to use her surname when she spoke with 7.30.

"If felt like a bit of a let-down from the legal system," she said.

"There was information out there … I hadn't concocted anything or done anything wrong — I just took a real life, real-time recording and for some reason, they were saying that that couldn't be heard."

Cassie has now left Ambulance Victoria.

Jojic and Spadara 'were ice addicts'

During Ms Johnson-Portelli's case, Mr Jojic gave evidence that he was just an "occasional" ice user and that he had only ever fired guns at a shooting range.

Jojic, the acquitted, has since pleaded guilty to assault over a dispute about the drug ice. ( Supplied )

The jury was not told that Mr Jojic was facing charges of assault which resulted from a dispute over a share of ice, because that information was considered prejudicial.

He pleaded guilty this month to stabbing a man repeatedly during that dispute, leaving 20 knife wounds.

Mr Jojic's defence team questioned Mr Spadaro heavily over his criminal record and drug dealing.

Mr Spadaro's father Nick told 7.30 the pair were inseparable.

"They were ice addicts. I mean, what do ice addicts do? I can tell you, nothing's legal … My son was no angel," Nick Spadaro said.

"They did the dirty work for others and that's what they were."

The jury also did not know that another young man had come forward to police and alleged that his brother had told him that Mr Jojic had gone to their home on the night of the shooting and confessed that he had shot a girl.

It was also alleged that his brother had told the same thing to Mr Spadaro's mother, Julie, two days after the shooting.

"He was telling me that Jovan [Jojic] went around his place the night Sarah got shot," Mrs Spadaro said.

"And [he said] Jovan was panicking and saying, 'I didn't know the gun was loaded'. He kept just saying 'I didn't know it was loaded, I didn't know it was loaded'."

The Spadaro family notified homicide detectives about this conversation but it was not allowed into the trial because it was hearsay.

The brother who could give direct evidence about his conversation that night with Mr Jojic refused to speak to police.

Ms Johnson-Portelli's mother, Barbara Johnson, is hoping the brother who could help police will appear at a coronial inquest.

An inquest could spark Victoria's first retrial under the state's new laws providing an exception to double jeopardy laws, which would allow someone who has been acquitted to be re-tried for the same crime.

"I don't want to beg, I just like to hope that people had enough compassion in them to come forward and speak if they knew something," Ms Johnson said.

"It's not for nothing or for nobody, it's for somebody. It's for somebody who meant a lot to a lot of people. She deserves justice."

Mr Jojic and his lawyers declined to speak to 7.30.