The court heard evidence on Wednesday that authorities only began taking prisoners' temperature that day, and overcrowding and inadequate cleaning created the risk that the virus would spread quickly if it entered the prison.

Delivering his judgment on Friday, judge Timothy Ginnane said that prison authorities had "prima facie" failed in their duty of care for Rowson's health, through "a number of breaches of hygiene" in his unit.

Justice Ginnane ordered the Department of Justice and Community Safety to conduct a thorough assessment of COVID-19 risks at Port Phillip Prison, a measure he said would benefit Rowson, other prisoners and the broader community.

He ordered the assessment be completed by May 15. The prison's operator G4S will be responsible for implementing any changes.

The threat posed by the virus remains real, Justice Ginnane observed.

"Although the number of new cases of infection has decreased in recent days, the ongoing risks from the virus are shown by the continuing lockdown in Victoria which largely confines citizens of a free society to their homes and which shows no signs of ending," he said.

Rowson had sought to live in a bungalow at his mother's property during the pandemic.

An expert's report tendered to the court estimated Rowson had a 10 per cent chance of developing a severe form of COVID-19 if exposed to the novel coronavirus, and a 30 per cent chance of dying if that occurred.

But Solicitor-General Kristen Walker, for the Department of Justice and Community Safety, said no Australian prisoner had tested positive for coronavirus, which was the best evidence she could offer that authorities' efforts to prevent coronavirus entering prisons were working.

There would be no way to contain the virus in the event of an outbreak in the prison network, Mr Nekvapil said, and Rowson's instructions were that he could not be safe from the coronavirus in prison.

Ms Walker accepted the virus would spread more rapidly in prison than the community, but said authorities had taken steps to ensure the virus did not enter the system in the first place, and those steps were working.

This included quarantining new prisoners for 14 days before they were admitted to jail. Prisoners are not receiving visitors, and the time they are allowed out of their cells has been halved.

Rowson was sentenced to more than five years' prison in December 2018 for defrauding his terminally ill friend of 40 years, fraudulently taking out almost $300,000 in loans and credit cards in his dying friend's name.

He is eligible for parole in March 2022.

Justice Ginnane said the time Rowson had left to serve, the uncertainty about how his release would be managed, and the fact the virus had not entered the prison did "not favour" Rowson's release from prison.

Rowson has also lodged an application through the prison system for early release, which is yet to be determined.

Monique Hurley, a senior lawyer with the Human Rights Law Centre, which, with Fitzroy Legal Service, brought the case, said the decision shows the Victorian government was not doing enough to safeguard people in prison against COVID-19.

"Everybody deserves to be safe during a pandemic. But prisons are overcrowded and have substandard hygiene practices at the best of times," she said. "Right now, they are a COVID-19 tinderbox."