This is NOT just for his own peace of mind, but to ensure that Naku is vindicated in front of the whole family. Dutta is expecting Supriya and Ravi to admit to setting Naku up, but little does he know who truly is behind it. I think he also wants to punish them for all the pain they've caused Naku and him.
This is the only way I can think of where Ridhi would come back for a guest spot.
What do you think?