No one is under any legal obligation to heed your paid pathologist's opinions at all.
As I have repeatedly mentioned,you cannot force anyone to do anything here. You can stomp your feet and hold your breath, but that's about it.
If you feel you have enough to identify someone who is responsible for the theft or death, you can sue them if you have standing. Maybe you can also bring your proof to the media and see if anyone there will help you rattle some cages. But,ultimately, you cannot force anyone to investigate this as a homicide.