Weinreb said that Dzhokhar Tsarnaev waited four minutes after he arrived at the explosion point before detonating the bomb, which he had left next to a row of children.

Weinreb claimed that in the days after the bombing, the defendant showed no remorse. 20 minutes after the bombs exploded, the Tsarnaev brothers drove to Whole Foods and purchased a gallon of milk, according to Weinreb. Also after the bombings, Dzhokhar Tsarnaev posted on Twitter that he was “a stress free kind of guy.”

“He acted like he had not a care in the world,” Weinreb said. “He acted that way because he believed that what he had done was good.”

The two sides disputed exactly how the younger Tsarnaev came to participate in the crimes. While the prosecution said that Dzhokhar Tsarnaev “self-educated” with terrorist materials he found online, the defense said that he was heavily influenced by his elder brother.

Clarke, one of Dzhokhar Tsarnaev’s lawyers, began her opening statement by addressing the emotional toll of the case. She referred to the crime as “misguided acts carried out by two brothers—26-year-old Tamerlan and his 19-year-old brother.” Throughout her defense, she argued that Tamerlan Tsarnaev led and planned the alleged attacks.

“[Dzhokhar’s] path was born by his brother, created by his brother, and paid for by his brother,” she said. “Unfortunately and tragically, Dzhokhar was drawn into his brother’s plan ... and that led him to Boylston Street.”

Members of the public and journalists watched the proceedings by television in two overflow courtrooms. Examinations of witnesses followed the opening statements.

Months before the bombing, Dzhokhar Tsarnaev worked as a lifeguard at Harvard’s Malkin Athletic Center. He attended the Cambridge Rindge and Latin School, just a few hundred feet away from Harvard’s campus.

—Staff writer Samuel E. Liu can be reached at samuel.liu@thecrimson.com. Follow him on Twitter @samuelliu96.