I agree but at the same time, I think we have to look at this from Jonah's POV. If your beloved biological son was critically injured and you are praying to god he'll recover from brain death, you might be more concerned with his life than you are with the adult who was overseeing your son. Most people blame the adults when their child is injured on the adult's watch. I'd be enraged at Rebecca too.
On the other hand, if he genuinely loved Rebecca and wanted to marry her, he would have also been devastated over her death and also viewed that the police slanted the investigation as a suicide was way beyond ridiculous, outlandish, unprofessional and illogical. He would have been outraged at the injustice with which the police mistreated and disrespected Rebecca's body in death - unless he blamed Rebecca for his son's brain death and subsequent death.
If his rage at Rebecca for his son's accident outweighed his love for her, he might have felt she deserved to be dead and just wanted her death to be over with so he could deal with the loss of his son. I would say the same for Dina except that after Rebecca was dead, Dina persisted in her vendetta for YEARS against not only Rebecca but also Rebecca's teen sister, which alludes to how intense and obsessive her hatred and contempt towards Rebecca was to begin with. Now Dina is claiming she never believed Rebecca had anything to do with her son's death, which on its face is laughable and hypocritically ironic.
I still have my own informed opinions about who did what to Rebecca.
There is a lot of circumstantial evidence against Adam, but there is also a lot of psychological and scientific evidence which point towards the person who shall not be named whom I believe is the actual premeditator and perpetrator. Adam may have been involved in the murder, but he was a FOLLOWER, not the leader.
I believe in justice and the perpetrator will be justly and duly punished, if not on earth, in purgatory and hell. Good luck to the who thinks s/he got away with murder.