Anirban Bhattacharya, who is essaying the role of rape-murder convict Dhananjay Chatterjee, said it was a "psychological recce" for him when the actor visited his family before they started shooting.
Dhananjay was hanged to death in 2004.
"I had visited Dhananjay's family at Chhatna in Bankura as part of psychological recce and felt how a single incident could fill up the minds of the family members with bone- chilling darkness.
"We met his siblings. I will not comment whether he really committed the crime or not, but we were definitely affected after seeing the condition of the members of his family and how they are still coping with the incident of hanging," Anirban said.
The actor also visited the cell at Alipore Central Jail where Dhananjay was kept in the run-up to his hanging and called it "an experience beyond explanation".
"I visited the cell and interacted with some of the inmates who were his companions in those days. It will be difficult to measure if these two experiences directly played any role when I gave the shots, but I had to keep those in mind while performing," he said.
Anirban added he was unsure if his portrayal had any similarities with the rape-murder convict.
He, however, added, "I will never replicate Dhananjay, but would rather bring out the person within (him). After certain scenes I felt feverish and drained out."
Actor Anusha Viswanathan, daughter of director Ashok Viswanathan who enacted the victim's character in the movie said, "Director Arindam Sil initially asked me to visit his office in school uniform. Then, he told me that I would play the role in his film. He asked me to study about the incident from media reports and two books written on the episode.
"I can't possibly imagine what she went through in real life. I had to think that I am not that character. I felt I would not be able to essay the role if I would be more emotionally involved."
Anusha said she was "scared" while enacting the scenes that involved her character with Dhananjay's.
"I was scared as I knew what the scene was going to be like. But I kept in mind I was just portraying a character like Anirban, who seemed to enter a zone before the shoots and interacted little."
Talking about the movie, Sil said, "We are never saying whether Dhananjay was guilty or not. We have only made the film based on writings from research work on the events leading to his hanging in 2004 and the aftermath.
"We are tracing back the events of 1990 when the victim's body was found. After my visit to his native place Chhatna recently, I had an uncanny feeling that Dhananjay was staring at me and wanted to say many things. I am projecting this Dhananjay as I see, and not the Dhananjay we read in papers."
The film hits the screens on August 11.