An aged care provider has been found not guilty of placing residents at risk by not properly training its staff before a deadly COVID-19 outbreak.

Heritage Care faced a County Court jury trial after 34 residents died at its Epping Gardens home, in Melbourne's north, in July 2020.

It was charged with breaching the Occupational Health and Safety Act, between March and July of 2020, by failing to ensure the workplace was safe and without risks to health.

Crown prosecutor Garry Livermore KC argued Heritage failed to reduce risk at Epping Gardens, as not all of its workers were trained and assessed in using personal protective equipment (PPE) before the fatal virus outbreak.

"All you need is one worker not to use the PPE properly, the risk is that the virus spreads with catastrophic consequences in an aged care facility of this kind," he told the jury, when the trial began on August 26.

However, Heritage Care's barrister said it denied the charges and asked the jury to question whether training and assessing 100 per cent of staff would have actually reduced risk of the outbreak.

"It's not about perfection, because anyone can be perfect after the event, we all know about the dangers of hindsight," Daniel Gurvich KC told the jury.

He said staff were expected to share knowledge, training and experience with each other, and the COVID-19 outbreak had nothing to do with PPE training.

The jury returned on Friday afternoon and found Heritage not guilty of the single charge.

There were gasps in the courtroom as the verdict was handed down.