In an oblique reference to the Delhi gangrape case, he said, "I am not for letting them (culprits) go."
"Death sentences do not serve as a deterrent and its efficacy as a capital punishment is doubted based on empirical grounds and is not a preventive function," Sen said addressing a seminar on 'Realisation of Justice' organised by the Calcutta high court in Kolkata.
Sen said, in India, awarding of death sentences was much lower than China where it was the highest in the world.
"In India, death sentences are awarded, but not executed except for recently in the case of Mumbai attacks," he said.
"I am not against severe punishment in case of critical cases," he added.
In the course of his lecture, he also referred to the Sanskrit play Mrichhakatika (The Little Clay Cart) where Charu Datta set the criminals free instead of punishing them.
"The play showed that tit-for-tat justice does not bring well to the world in the realms of prosperity, happiness and security for all," Sen said.