Mthethwa was found guilty of the 2013 murder of sexworker Nokuphila Kumalo, in the Western Cape High Court in March.
He is due to be sentenced on Thursday.
Mthethwa’s attorney, William Booth, said the artist could face an “uphill battle” to get permission to create art from prison.
Booth spoke to Weekend Argus and said he believed Judge Patricia Goliath was “incorrect in convicting (Mthethwa) for murder”.
“I am going to be applying for leave to appeal against his conviction once he is sentenced. I will also be applying for bail to be fixed for him, pending the finalisation of his appeal.”
Mthethwa remains in custody after two failed bail applications.
Booth said if he failed with both the bail appeal and leave to appeal against Mthethwa’s conviction, he hoped the artist would be granted permission to continue with his art in prison.
“We hope he will be outside and be able to carry on with his work.
“In prison, I don’t know what they will allow and what they won’t allow one.
“Hopefully they will allow somebody to continue with their work.”
However, if Mthethwa is able to produce work in jail, he may face challenges in getting it sold.
South Africa’s fine art auction, Strauss & Co, has already opted to stop auctioning the artist’s work.
Marketing and advertising officer Bina Genovese said: “In a recent board meeting, the directors of Strauss & Co decided that the company would not be auctioning works by Zwelethu Mthethwa until further notice.”
Booth added that despite local galleries remaining unwilling to display or sell Mthethwa’s art, some of his pieces remained features in international galleries.