New proof on an old case?

my friends brother got sentenced to 50 years tdc for agg ault back in 2000 or so and his mother has a notarized letter from his wife who pressed charges on him stating that she was lying and put her signature on it. Mind you , he has already done 10 years or so. What does he need to do to try to get released after 10 years? I understand about appeals but if you can give me more information on this particular situation it will be greatly appreciated. thanks. best answer 10 pts