Hi,
The episodes show that forensic science maynot be needed to solve this mystery. ACP Ragini is doing things the way Sherlock Holmes used to solve. She has not been shown speaking to the doctor who was the last person to see Tripti alive.
Tripthi on gaining conciousness had said that to the doctor"How could the killer do this to me. I need to talk to killer and I wont spare the killer" It indicates that it someone whom Tripti had trusted. Meaning the killer was not her enemy. This means that it maynot be the Viranis.
Also it looks a bit difficult to beleive that only the first word before Virani is smudged. It could be that the killer had noticed that Tripti writting the name of the killer on the diary. The killer would have smudged out the first letter by force on the dying Tripti. Then with the very same finger of Tripti which carried the blood forced her to write Virani name and completed the balance of the sentence to put the blame on the Viranis.
Tripti had shown finger towards the Viranis, but the killer could have been standing behind the Viranis.I feel this is what must have transpired in that few minutes before everyone saw Tripti dead.
Any takers for this theory?? If you have a theory please let us all know.
Also what Mihir said is true, that when Tulsi kills it is termed as Moksha, and when some one else kills Tulsi calls the killer a murderer. It is like killing an enemy soldier for which the army men are awarded and life sentence for a person who kills a normal civilian even though he might be a bigger enemy in mask.