The wife of slain drug lord Carl Williams is appealing against a court order to sell off the Essendon house, which is worth more than $1 million.

Carl's father George Williams, when he died in 2016, bequeathed the home to his granddaughter Dhakota, who lives there with her mother Roberta.

But the Australian Tax Office, owed about $740,000 in unpaid taxes from George, launched a legal battle over George's will.

Earlier in 2018, the Supreme Court ruled Roberta had no claim to the house and made orders for it to be sold and the proceeds used to pay the debt.

But Roberta has launched an appeal and on Friday her pro bono barrister John Selimi fought passionately on her behalf.

"This is a quest for justice from the graves of George and Carl Williams," Mr Selimi told the Supreme Court.

The barrister said Roberta was unable to attend an important prior court hearing over the matter because she was sick in hospital.

At that court hearing an application for a summary judgment was made to have the matter resolved without a trial, and Roberta was not there to advise her lawyer.

"Every party has a right to be present when his or her matter is heard," Mr Selimi said.

"It is not in the interests of justice for an application for summary judgment to be made when a party was an inpatient suffering from an intractable migraine."

Roberta claims that George's tax debt should have been wiped under a 2009 deal struck with Victoria Police.

As part of that deal Carl provided information to police about a series of murders committed during the "underbelly war" between 1999 and 2006.

But Carl was bashed to death inside Barwon Prison in 2010 before he could testify in court.

Victoria Police later cancelled their offer to to pay George's tax debt.

In 2013 George agreed to mortgage the home to the ATO in a settlement deal.

After he died in 2016 the ATO came after it, but Roberta refused to sell, sparking a legal battle.

Roberta argued her grief-stricken father-in-law was coerced into entering into an agreement with the ATO.

But the matter was never tested at trial and was resolved by the court order that Roberta is now appealing over.

"It is an absolute right for every person to have their day in court, to expose their truth," Mr Selimi said.

"Rather than sweep the case under the carpet ... and sell their home and kick them out on the street.

"That's not justice."

The appeal hearing will continue on Tuesday.

Australian Associated Press