The number of aged care residents who died during COVID-19 outbreaks in Melbourne raises questions about whether one facility could have prevented dozens of casualties through bolstered training, a lawyer says.

Victoria's workplace regulator is prosecuting Heritage Care, which is the parent company of Epping Gardens aged care home, after 89 residents and 65 staff contracted COVID during a 2020 outbreak at the facility.

Thirty-four residents died from the virus or related complications.

University of Sydney infection prevention and diseases control clinical chair Ramon Z Shaban argued all staff should have received personal protective equipment (PPE) training at the facility after authorities declared COVID a public health emergency.

Even previously trained staff should have completed it, and the training should have included practical components where workers had to physically demonstrate their competency, he contended in court documents.

When staff inappropriately or insufficiently used PPE, the risk of infection was "certain", Professor Shaban said.

Only about 35 staff completed a hand hygiene and PPE audit before the July outbreak at Epping Gardens, prosecutors allege.

Defence barrister Neil Clelland on Tuesday said significant COVID outbreaks were "commonplace" at aged care facilities in 2020, and Epping Gardens wasn't an outlier in terms of what proportion of residents died.

The figures from other fatal aged care outbreaks suggested either a multitude of facilities were not complying with the supposed "best practice", or PPE and related training was ineffective in preventing an outbreak, he said.

Prof Shaban said WorkSafe did not ask him to consider the circumstances of aged care facilities comparable to Epping Gardens in Victoria, but he drew on published evidence and documentation to inform his opinions.

Mr Clelland said: "Can I suggest to you that the best evidence is staring at you in the face?"

The Aged Care Quality and Safety Commission assessed Epping Gardens' preparedness for an outbreak ahead of its first confirmed COVID case on July 20, 2020.

It found the home's policies were clear and concise, its training systems were robust and the staff knew what they were doing, former Epping Gardens general manager Alistair Cooray told the Melbourne Magistrates Court on Tuesday.

He agreed it gave him confidence the facility was well prepared for an outbreak.

Mr Cooray conceded there was no reason training about PPE couldn't have been mandatory for all staff.

Prosecutors put to him that all staff including hospitality and volunteer workers had to understand and be competent in infection control guidelines as per official guidance.

He agreed that would have included being able to understand how to properly use PPE.

WorkSafe alleges Heritage Care failed to provide and maintain a working environment that was safe and without risks to health between March 13, 2020 and July 20, 2020.

The watchdog alleges the company did so by failing to provide the necessary training to staff and failed to ensure residents were not exposed to health and safety risks.