Claire Blackman, 42, said her husband Sergeant Al Blackman, 39, "bitterly regrets" the incident which saw him jailed for life for killing the insurgent in Helmand province in 2011.
Lord Chief Justice Lord Thomas and two other senior judges are to hear Sgt Blackman's appeal against his conviction and sentence.
"I still hope, because I have to, that his conviction will be overturned. I recognise that it would be a very difficult decision to make," Mrs Blackman said.
Mrs Blackman, a marketing executive, was interviewed for the documentary by Chris Terrill, a former Royal Marine, which is being shown tomorrow night on BBC1 ahead of the appeal.
Sgt Blackman was jailed for life and told he would have to serve at least 10 years' imprisonment.
The documentary, Marine A: Criminal Or Casualty Of War? is on BBC1 tomorrow night.