How Did Daniel's Death Come About?

Port stiene was charged with all four murders, because now he can be linked to all four victims. Jack taylor's sisters decide to do some investigating of their own. And they start to make better connections between the death than the police had. Then port is finally identified on c c t v with jack near barking station shortly before his death. The apparent suicide note and bed sheet found with daniel whitworth is now finally examined, and ports diane is found. But this is crazy to me. They had port stiene before because he was arrested, he went to jail, and then was out on remand for perverting the course of justice in the case of an