Thank you for your question.
You have said that David is waiting for his trial for his criminal matter.
I do not understand why his deportation would be 'very much on the cards' when his trial has not commenced. I am not a criminal solicitor, but i am sure the court will decide if he is guilty or not. If found guilty, he may have to serve his sentence. Once he is serving his sentence or has completed his sentence, the Home Office will then contact him in order for him to make representations as to why he should be allowed to stay in the UK. It is important that factors as to why he should stay in the UK and why he cannot return to South Africa are given to the Home Office. It is based on these representations, that the Home Office will decide if they want to take any action against David. This is a very complex area and I would strongly suggest that you discuss this fully with your solicitors.
I wish you all the best for the future.
Please kindly rate my answer.