The Boston Marathon bomber death penalty trial continued on Thursday as lawyers representing Dzhokhar Tsarnaev pushed to bring a Roman Catholic nun and renowned death penalty opponent to testify as a star witness.

Last month, the 21-year-old convicted terrorist was found guilty of 30 charges for his role in the 2013 Boston Marathon bombings, including conspiracy to use a weapon of mass destruction and bombing a public place. The charges also covered a carjacking that took place in the aftermath of the attack, the deadly shooting of a Massachusetts Institute of Technology police officer, and a gunfight in Watertown, Massachusetts, in which Tsarnaev and his now-deceased brother tossed explosives at police.

The start of the trial was delayed Thursday as defense lawyers petitioned the court to bring Sister Helen Prejean to take the stand, reports USA Today. The high-profile death penalty activist received international fame through her book, "Dead Man Walking," which was translated into a movie under the same name in 1995. It starred Susan Sarandon and Sean Penn.

However, court records show that prosecutors told Judge George O'Toole Jr. that they would argue to exclude her testimony and that she should not be allowed to take the stand. A decision of whether or not Prejean will be allowed to give a testimony was left undecided.

The defense is expected to rest its case on Monday. Afterward, the prosecution will have a chance to make a rebuttal before both sides deliver their closing arguments.

The 76-year-old nun was seen in the federal court building Thursday, entering a room used by defense lawyers, reports The Associated Press. She began a prison ministry in 1981 in New Orleans, and it noted for working with Patrick Sonnier, a death row inmate who had been convicted of killing two teenagers.