But after the first week of the defense case, a little part of me feels sorry for the person he could have become. Yes, he did terrible things and hurt a lot of people, and I do feel a whole lot worse for them.  I'm haunted by Krystle Campbell, Lingzi Lu, Martin Richard and Sean Collier and the lives they didn't get to finish. But I wonder whether Tsarnaev is haunted, too.  It's impossible to say because he just sits at the defense table like a lump, no matter who is on the witness stand. It could be his best friend or the loved one of someone he blew to pieces. The visible reaction is the same: zero, zip, nada.  Prosecutors would say he feels no remorse. They see him as the defiant punk who flipped the bird at the camera in a holding cell at the courthouse the day he was arraigned for setting off bombs at the 2013 Boston Marathon.  But after watching him in court for most of this year, I'm not sure he feels anything. It's like he isn't there. He's not a monster, he's a cipher. Nothing seems to get a rise out of him.  Hearing a bit of his story as the defense builds its case for why the jury should spare his life, it's easy to see how Tsarnaev learned to get by in a chaotic family by becoming agreeable to the point of being invisible.  His teachers loved him. Five came to court and testified on behalf of a boy who grew up to be perhaps the most hated man in Boston. They remembered him as smart and sweet-natured, with shining brown eyes. It's so clear he had potential, and that's another tragic element to a case already overloaded with tragedy.  The defense showed how even his own mother, Zubeidat, undermined that potential. She let her own pride get in the way.  A teacher told the story of how Zubeidat Tsarnaev pulled her son out of a prestigious charter school known for getting its students "full-ticket" scholarships to good colleges. Why? She was angry he'd been sent home for wearing the wrong color of pants. Jahar wore blue pants, and the family was too poor to buy him a brown pair, his mother said in an angry phone call to the school.  The teacher asked Jahar, as he was known, whether it would help if she called and talked to his mother. No, please don't, he responded. He was starting the ninth grade, and he'd already learned not to make waves at home.  Zubeidat was flashy and loud and demanded attention. She was over the top in her ambitions for her oldest child, Tamerlan. He was going to Harvard, she'd brag. He was going to box in the Olympics. Of course it didn't work out that way.  We didn't hear a peep about her hopes for her youngest, Jahar. The landlady came to his middle school graduation.  There were photos of Tamerlan and his father, Anzor, at boxing matches, but none of Jahar with his father. Tamerlan's boxing coach remembers Jahar following his big brother around "like a puppy."  Both Anzor and Zubeidat seemed to grow old before their time, their landlady's son recalled. Anzor seemed always to be in pain. Zubeidat began to cover herself in traditional Muslim clothing.  But she still craved attention. At a baby shower for her American-born daughter-in-law, Zubeidat sat in the kitchen like she was queen bee, talking about religion, said Judith Russell, the baby's other grandmother.  Russell's daughter, Katherine, dropped out of college and married Tamerlan Tsarnaev. She had met him at a nightclub and fell hard.  The defense displayed a photo of the couple, strolling hand-in-hand. The leaves on the trees were turning gold and the scene looked like a Hallmark card. But Tamerlan proved to be a toxic force in the life of a young woman who had been blond, pretty and outgoing.  He came between "Katie," as she was called, and her family. Judith Russell said her daughter became isolated. Tamerlan's presence in her life also created distance with her best friend since childhood, Gina Crawford.  Tamerlan was unfaithful more than once, and he may have been violent with Katie, who converted to Islam and changed her name to Karima Tsarnaeva. She was the breadwinner. But when company came for dinner, she cooked, served the men and then retired to another room. When people saw them on the street, she invariably walked a few paces behind her husband.  By then, Anzor and Zubeidat were splitting up. Mother and son were delving deeply into radical Islam -- and coming to the attention of authorities in Russia and the United States.  Tamerlan headed to Russia for six months, looking to join the holy warriors of jihad. They called it "going into the forest." He left his bride and baby behind. On Katherine's MacBook laptop, authorities later found searches for information about "rewards" for the wives of martyrs and holy warriors.  But people who care about Katie Russell insist she had no idea about her husband's plans to bomb the finish line of the Boston Marathon. She isn't on anybody's witness list, and she hasn't been charged with anything.  After Tamerlan returned to Cambridge, his parents headed to Russia -- separately. They're still there, and aren't expected to make an appearance at the trial.  That left Tamerlan, the eldest son, as the head of a family that included his wife, daughter and brother Jahar. While his wife worked, Tamerlan spent his days at home, sending his wife and brother emails with attachments of videos and lectures he found on al Qaeda websites.  Jahar went off to college at the University of Massachusetts Dartmouth, some 60 miles to the south. None of his friends had a clue about his extracurricular activities in the world of radical Islam. They knew him from "Bro Nights," the regular off-campus gatherings of a close group of friends from Cambridge.  The defense says Jahar was trying to build his own life, but was becoming unmoored. He was flunking out of school. And he was still in Tamerlan's toxic orbit.  For the first couple of days of the defense case, it seemed like we'd been transported to another courtroom and another trial -- United States of America vs. Tamerlan Tsarnaev.  Once again, Jahar seemed like an afterthought at his own capital murder trial, just as he had been throughout his life.  Even after he was shot up and handcuffed, his first question was: "Where's my brother?"  Tamerlan was the martyr. He made sure of that. He walked into a volley of police bullets. When he ran out of bullets, he hurled his gun at a cop. And then he was run over by Jahar, who was trying to escape in a stolen Mercedes SUV.  Toward the end of an abbreviated week of testimony, the defense started to change up the story line, presenting people who thought they knew Jahar and cared about him. Two young women who were part of his "Bro Night" gatherings testified for him and then cried as they stepped down from the witness stand.  The last time they were all together, it was spring break two years ago. They were shooting off fireworks from Jahar's backpack along the banks of the Charles River. Jahar was dancing through the sparks.  "He was being really silly," said 21-year-old Alexa Guevara. And then she stepped off the witness stand and started to sob so loudly that people in the courtroom could hear her from the hallway.  And that's when I felt sorry for Jahar -- and for anybody who ever cared about him -- because genuine tragedy comes in more than one dimension. Three of his college "bros" may be starting their adult lives in federal prison because they cleaned out his dorm room and helped ditch his backpack and laptop.  The sad truth is, Jahar probably wouldn't be on trial for his life if not for his big brother. People wouldn't be arguing over whether he should live or die. He'd probably be off somewhere getting stoned, playing FIFA video games on Xbox and thinking it's been a while since everyone got together for "Bro Night."
CNN's 13th juror, Ann O'Neill: Dzhokhar Tsarnaev's lost potential is yet another tragedy in the Boston Marathon bombing.