Who is Old Hunter from Death of a Red Heroine and what is their importance?

Old Hunter is Yu's father. He is a retired policeman and plays the political game rather better than his son. Old Hunter is instrumental in breaking the case open. He knows how to operate within procedure and outside of it and has his finger on the political pulse of every situation. As a volunteer traffic officer, he is perfectly placed for Chen to be able to hire him without suspicion in order to break Wu's alibi. Old Hunter is a cop through and through. He is almost embarrassed to take payment for his help. It is the thrill of police work that gives him satisfaction.