Peter Ellis' former lawyer says his appeal could be ground-breaking.

Almost a year since Ellis died, the Supreme Court has ruled his appeal can go ahead.

Ellis was convicted on 16 charges of sexual offending against seven children in 1993.

Nigel Hampton QC told Heather Du Plessis-Allan the appeal was probably issued not just because of tikanga Maori - to restore mana after death.

He says Parliament gave pardons in 2000 to soldiers shot because of cowardice in World War one.

"Part of the reason for passing that legislation was the fact that this was a continuing slur on the reputation and mana of the particular families, so it is not just a Maori concept."

Hampton says the irony is that Ellis had to die to possibly win a case and set a precedent.

While alive, Ellis appealed twice to the Court of Appeal, the second time after a referral by the Governor-General.

The first appeal quashed three of his convictions.

The second appeal against the remaining 13 convictions was dismissed in 1999.

Ellis was granted leave to appeal those remaining convictions in July last year, but died in September.

The Supreme Court says the reasons for this decision will be provided at the same time as the decision is released on the substantive appeal.