The man in the coma is the old police boss, who is married to the black CPS girl. He was having a fling with another black girl who saw him being mowed down by a car.
This girlfriend has been seen in the episode sat in her car outside the hospital, gazing wistfully at his ward window. His wife suspects he was having an affair but doesn't know who with.
Because the police boss is in a coma, his replacement has been drafted in to team - the chap who was in Hustle.
The only connection we can tell to date between the murder victims is they are all of the Abrahamic religion - Jewish, Muslim and Christian. They had lifestyles that could be linked to the end of the world as predicted in the holy books of these three religions.
How the girl claiming to have been abused by her father fits in, I have no idea.