I got interested in this when the film came out.
I thought the law was good - if you have a man in a military prison, and if the Huns attack, and he gets a gun and goes chugga chugga chugga, killing a few of them
then he is forgiven his crime
However the film is not what happened necessarily
There was a good tv prog on this, about 20 years ago as well, and that has not been repeated - the Bushveld carbineers seem to have been a bit like the Cossacks so to speak
I dont think we have enough evidence to decide but I admit I thought he was a scape goat of the empire !
I thought the solicitor/military man had written a book about it, but that does not seem to be the case. I think he would have if he thought it unfair.