Why shouldn't his role be investigated? May be he didn't like the way his father treated his mother and that had a role in him feeling depressed? Why shouldn't he be tried for abetment of suicide?
Look how he changed his versions. First 40 days after death, no word against Rhea. Suddenly this abetment of suicide case against Rhea. Now after 40 more days, he says it's murder.
He needs to be grilled first.
There is something called greiving that can be done in the first 40 days. More evidence comes out and yes you come up with different conclusion. They trust the Mumbai police initially and than it was clear they were doing a sham investigation. That def got proven in the supreme court or else the case wouldn't have been given to the CBI. thus they asked the Bihar police to do a investigation based on what they knew. Based on what they knew they though it was abetment to sucide then. Yeah a sl*t who knew him for a year is more trustworthy than his father who educated and fed him. If he was a bad dad would Sushant had been the success he was. It was after he met Rhea he supposedly fell into depression.