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 hearing, the defendant arrived at the courthouse in a four-vehicle motorcade that included a van, a Humvee and a state police car.
A group of 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, 23, said she traveled from her home in Wenatchee, Wash., to attend the arraignment. Buckley said she has never met Tsarnaev but came because she believes he's 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 outside the courtroom 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.
Another ex-teammate, Shun Tsou, 20, of Cambridge, called Tsarnaev "a silent warrior type."
"There was nothing sketchy about him," said Tsou, adding that he had not formed an opinion on Tsarnaev's guilt or innocence.
Prosecutors say Tsarnaev, a Muslim, wrote about his motivations for the bombing on the inside walls and beams of the boat where he was captured. He wrote the U.S. government was "killing our innocent civilians."
"I don't like killing innocent people," he said, but also wrote: "I can't stand to see such evil go unpunished. ... We Muslims are one body, you hurt one you hurt us all."
Three people — Martin Richard, 8; Krystle Marie Campbell, 29; and Lingzi Lu, 23 — were killed by the bombs, which were improvised from pressure cookers. Authorities say the Tsarnaevs also killed Massachusetts Institute of Technology officer Sean Collier days later while they were on the run.
Numerous bombing victims had legs amputated after the two explosions, which detonated along the final stretch of the race a couple hours after the elite runners had finished.