(CNN)He was impressively polite and bright in the eyes of his boyhood teachers, an encourager of his college friends. He was a docile captured killer in the care of paramedics tending to his gunshot wounds. Dzhokhar "Jahar" Tsarnaev's defense team is seeking to spare him from a death sentence for his part two years ago in the Boston Marathon bombings and murder of an MIT police officer. Having focused on his dead older brother, portraying Tamerlan Tsarnav as harsh, overbearing and bent on jihad, they now shift to the younger brother who tagged after him, as one witness said, "like a puppy." The sentencing phase of the federal case will resume Monday. The jury was sent home Thursday because a juror was sick. Tsarnaev was convicted April 8 on all 30 counts, including 17 that carry a possible death penalty. The defense's transition from one brother to the other begins in the ambulances that rushed the brothers from their respective final showdowns with police in Watertown, Massachusetts, on April 19, 2013. Boston bombing survivor: I am not limiting myself . Tamerlan, dying from gunshot wounds and having been run over by the car his brother was driving as he fled, became combative in the ambulance. A paramedic testified Wednesday that it was common for patients in shock to become agitated and fight back. "He had an abdominal wound, it was an evisceration," said paramedic Michael Sullivan. It was a "penetrating wound," with the intestines protruding. "Every time we tried hands-on, he resisted that type of treatment," Sullivan said. "He was yelling, loud, like an 'rrrrrrrr' type of thing. It was like he was trying to get out of the seat belts that were holding him on" the stretcher. Jahar, on the other hand, was cooperative after his capture hours later -- until a tourniquet was applied too tightly, said paramedic Laura Lee. He responded to questions, giving his date of birth and saying he was allergic to cats. And then he asked a question of his own: . "Where is my brother?" The defense showed a series of photographs that demonstrated how the brothers differed in size and age. The younger brother has been portrayed as someone who follows, rather than leads. One of Tamerlan's boxing coaches testified earlier that Jahar followed his brother around "like a puppy." The defense asserts that the Boston Marathon bombings never would have happened if it weren't for Tamerlan. They have portrayed him as obsessed with jihad, spending hours in his computer trolling al Qaeda-style websites. An uncle in Russia told the FBI that Tamerlan came there in 2012, expecting to find "jihad in the streets." Magomed Kartashov was questioned by the FBI after 40 days in a Russian jail. The FBI summary report of the interview was read in court. Kartashov said his nephew asked him if he had contacts with people "in the forest," as locals referred to the jihadists. Tamerlan's information came from the Internet, but he had surprisingly little knowledge of Islam, the uncle told the FBI. When he asked his nephew why he wanted to go to the forest, he responded that "jihad was necessary today," Kartashov told the FBI. "I told him to stop or he wouldn't make it to the next tree." Jahar, on the other hand, was portrayed in the testimony of five of his former teachers as a smart, sweet kid who worked hard and earned good grades. He was "super kind, extremely smart, a very hard worker, really a lovely person," said Tracey Gordon, his fifth-grade teacher at Cambridgeport School. "All the teachers loved him," said Becki Norris, who had Jahar in her seventh-grade class at Community Charter School, a middle school in Cambridge known for setting its students on the path to "full ticket" scholarships to good colleges. "He was one of our top students, and one of our top athletes," Norris said. "He wasn't a rebel. If you asked him to do something, he'd do it. Like most middle-schoolers, he's need a little push, but he needed just one. " But after just a few days in the ninth grade, Jahar's mother pulled him out of the school and sent him to Cambridge Rindge and Latin, a large public high school. She was angry that her son had been sent home to change out of his blue pants. "She was very, very angry because he didn't have clean pants that matched the uniform and they didn't have the money," Norris said. "I thought he liked the school, and I didn't think he wanted to go." Norris said she asked Jahar if she could call his mother. "He flatly said, 'No, don't call her.' " He made friends in high school, and a core group got together regularly for "bro nights" during their freshman year at the University of Massachusetts Dartmouth, two young women testified. They smiled at Tsarnaev from with witness stand, but while he seemed generally more animated in court, he maintained his usual flat expression. "He was loyal, fun, laid-back," said classmate Tiarrah Dottin. She said she had no idea he was listening to jihadi songs or watching al Qaeda videos on his laptop. She bowed her head and wiped tears from her eyes as she stepped off the witness stand and took a seat in the audience. Alexa Guevara testified that Tsarnaev "was private about his family," and did not discuss politics or religion with her. She said when he spoke about the future he said he planned to transfer to the University of Massachusetts Amherst and study marine biology. He was a supportive friend, she added. "He encouraged me to go to art school," she said. She showed him her sketches, and he thought they were good. "He said I had talent and shouldn't let it go to waste. I should go to art school and do what made me happy. It made me feel really good, like somebody believed in me," she said. She ended her testimony with a memory of one of the last times she saw Tsarnaev and the "bros." It was March 2013, during spring break of their sophomore year. They went out to eat and then drove to a spot by the Charles River. "Jahar went over to his car, and he got a backpack and there were fireworks inside," she recalled. "He set one up and ignited it. It didn't work. The second one did work. We were all whooping and hollering. Jahar was jumping through the firework itself. He was being really silly." She sobbed as court recessed for the day, and her cries could be heard in the hallway outside the courtroom. Boston Marathon terror attack fast facts . CNN's Aaron Cooper, Ray Sanchez and Cameron Tankersley contributed to this report.
Defense seeks to make case to spare life of convicted Boston bomber Dzhokhar Tsarnaev.
Defense: Brother Tamerlan, who was killed during police showdown, was obsessed with jihad.
Dzhokhar Tsarnaev was well-liked, polite and docile, according to witnesses.