According to the New York Times, on Monday in the penalty phase of the trial, Sister Helen Prejean, testified: "He said emphatically, 'No one deserves to suffer like they did'".
Sr Prejean (76) also spoke about the tone of his voice: "It had pain in it, actually, when he said what he did about 'nobody deserves that.' I had every reason to think he was taking it in and he was genuinely sorry for what he did."
The nun provided to jurors the first evidence of Tsarnaev feeling regret since he was captured and charged two years ago with the killing of three people and the wounding of 264 others, as well as the death of a police officer during the ensuing manhunt.
Describing five meetings she has had with the defendant since March at the defence team's request, Sr Prejean portrayed Tsarnaev as respectful and receptive to her, even though he had probably never met a Catholic nun before.
The jury convicted Tsarnaev (21) last month of all charges against him. The government, which rested its case last month, has argued for the jury to sentence him to death. The defence has said he should be sentenced to life in prison without parole.
Sr Prejean is a nationally recognised opponent of the death penalty, which the defence has argued makes her a witness with a strong bias.
