As survivors of the bombing looked on, Tsarnaev, 19, gave a small, lopsided smile to his two sisters upon arriving in the courtroom. He appeared to have a jaw injury and there was swelling around his left eye and cheek.
Leaning into the microphone, he told a federal judge, "Not guilty" in his Russian accent and said it over and over as the charges were read. Then he was led away in handcuffs, making a kissing gesture toward his family with his lips. One of his sisters sobbed loudly, resting her head on a woman seated next to her.
Tsarnaev, who has been hospitalized since his capture with wounds suffered in a shootout and getaway attempt, faces 30 federal charges, including using a weapon of mass destruction to kill, in connection with the April 15 attack, which left three people dead and more than 260 wounded. He could get the death penalty if prosecutors choose to pursue it.
The proceedings took place in a heavily guarded courtroom packed not only with victims but with their families, police officers, and members of the public and the media.
The Russian immigrant and former college student looked much as he did in a photo widely circulated after his arrest, his hair curly and unkempt. Wearing an orange prison jumpsuit, he appeared nonchalant, almost bored, during the hearing. The cast covered his left forearm, hand and fingers.
The bombing victims showed little reaction in the courtroom after a federal marshal warned them against any outbursts.
Liz Norden, the mother of two men who lost their right legs in the bombings, said afterward: "I actually felt sick to my stomach."
MIT Police Chief John DiFava, who was also in the courtroom, said Tsarnaev looked "smug."
"I didn't see a lot of remorse. I didn't see a lot of regret," he said. "It just seemed to me that if I was in that position, I would have been a lot more nervous, certainly scared."
DiFava added: "I just wanted to see him. I wanted to see the person that so coldly and callously killed four people, one of whom being an officer of mine."
Authorities say Tsarnaev orchestrated the bombing along with his older brother, Tamerlan Tsarnaev, who died following a gun battle with police three days after the attack. Dzhokhar Tsarnaev was arrested on April 19, hiding in a bloodstained boat in a suburban backyard after a manhunt that paralyzed much of the Boston area.
Tsarnaev is also charged in the killing of a Massachusetts Institute of Technology police officer and the carjacking of a motorist during their getaway attempt.
His two sisters were in court wearing traditional Muslim scarves called hijabs. One was carrying a baby; the other wiped away tears with a tissue. Tsarnaev's parents remained back in Russia.
Tsarnaev's lawyer Judy Clarke, an expert in death penalty cases, asked that the judge enter not-guilty pleas for him, but U.S. Magistrate Judge Marianne Bowler said: "I would ask him to answer."
On the same day as the arraignment, Boston's police commissioner appeared on Capitol Hill and complained to a Senate panel that the Justice Department failed to share information on terrorism threats with local officials before the bombing.
"There is a gap with information sharing at a higher level while there are still opportunities to intervene in the planning of these terrorist events," Commissioner Edward F. Davis III said.
Reporters and spectators began lining up for seats in the courtroom at 7:30 a.m. as a dozen Federal Protective Service officers and bomb-sniffing dogs surrounded the courthouse. Four hours before the 3:30 p.m. hearing, the defendant arrived at the courthouse in a four-vehicle motorcade.
About a dozen Tsarnaev supporters cheered as the motorcade arrived. The demonstrators yelled, "Justice for Jahar!" as Tsarnaev is known. One woman held a sign that said, "Free Jahar."
Lacey Buckley said she traveled from her home in Wenatchee, Wash., to attend the arraignment. She said she believes he is innocent. "I just think so many of his rights were violated. They almost murdered an unarmed kid in a boat," she said.
A group of friends who were on the high school wrestling team with Tsarnaev at Cambridge Rindge and Latin waited in line for hours, hoping to get a seat.
One of them, Hank Alvarez, said Tsarnaev was calm, peaceful and apolitical in high school.
"Just knowing him, it's hard for me to face the fact that he did it," said Alvarez, 19, of Cambridge.
Prosecutors say Tsarnaev, a Muslim, wrote about his motivations for the bombing on the inside walls and beams of the boat. He scrawled that the U.S. government was "killing our innocent civilians," and also wrote: "We Muslims are one body, you hurt one you hurt us all."
Martin Richard, 8, Krystle Marie Campbell, 29, and Lingzi Lu, 23, were killed by the two bombs, which were fashioned out of pressure cookers, gunpowder, nails and other shrapnel. Numerous victims lost legs.