The nun and death-penalty foe behind Dead Man Walking is due to testify in Dzhokhar Tsarnaev's sentencing trial today and defense attorneys hope she portrays the death penalty as an unjust punishment for the 21-year-old. Sister Helen Prejean, who developed a close relationship with Louisiana death row inmate Patrick Sonnier before his execution in 1984, is one of two witnesses left to testify for the defense, though federal prosecutors plan to file a motion to bar her from taking the stand, NBC News reports. With Prejean in mind, talk has already turned to where Tsarnaev would end up should he get life in prison.