BOSTON — Dzhokhar Tsarnaev was convicted on all charges Wednesday in the Boston Marathon bombing by a federal jury that now must decide whether the 21-year-old former college student should be executed.

Tsarnaev folded his arms, fidgeted and looked down at the defense table as he listened to one guilty verdict after another on all 30 counts against him, including conspiracy and deadly use of a weapon of mass destruction. Seventeen of those counts are punishable by death.

The verdict — reached after a day and a half of deliberations — was practically a foregone conclusion, given his lawyer’s startling admission at the trial’s outset that Tsarnaev carried out the terror attack with his now-dead older brother, Tamerlan.

The two shrapnel-packed pressure-cooker bombs that exploded near the finish line on April 15, 2013, killed three spectators and wounded more than 260 other people, turning the traditionally celebratory home stretch of the world-famous race into a scene of carnage and putting the city on edge for days. Tsarnaev was found responsible not only for those deaths but for the killing of a Massachusetts Institute of Technology police officer who was gunned down days later.

In the trial’s next phase, which could begin as early as Monday, the jury will hear evidence on whether Tsarnaev should get the death penalty or spend the rest of his life in prison.

In a bid to save him from a death sentence, defense attorney Judy Clarke has argued that Tsarnaev, then 19, fell under the influence of his radicalized brother.

“If not for Tamerlan, it would not have happened,” Clarke told the jury during closing arguments. Prosecutors, however, portrayed the brothers — ethnic Chechens who moved to the United States from Russia more than a decade ago — as full partners in a coldblooded plan to punish the U.S. for its wars in Muslim countries. Jihadist writings, lectures and videos were found on both their computers, though the defense argued that Tamerlan downloaded the material and sent it to his brother.

Tamerlan, 26, died when he was shot by police and run over by his brother during a chaotic getaway attempt days after the bombing.

The government called 92 witnesses over 15 days, painting a hellish scene of torn-off limbs, blood-spattered pavement, ghastly screams and the smell of sulfur and burned hair.

Survivors gave heartbreaking testimony about losing legs in the blasts or watching people die. The father of 8-year-old Martin Richard described making the agonizing decision to leave his mortally wounded son so he could get help for their 6-year-old daughter, whose leg had been blown off.

In the courtroom Wednesday, Denise Richard, the boy’s mother, wiped tears from her face after the verdict. The boy’s father, Bill Richard, embraced one of the prosecutors.

In Russia, Tsarnaev’s father, Anzor Tsarnaev, told The Associated Press in recent days that he would have no comment.

The others killed in the bombing were Lingzi Lu, a 23-year-old Chinese graduate student at Boston University, and Krystle Campbell, a 29-year-old restaurant manager. MIT Officer Sean Collier was shot to death at close range days later.

In a statement, Collier’s family welcomed the verdict and added: “The strength and bond that everyone has shown during these last two years proves that if these terrorists thought that they would somehow strike fear in the hearts of people, they monumentally failed.”

Some of the most damning evidence at the trial included video showing Tsarnaev planting a backpack containing one of the bombs near where the 8-year-old boy was standing, and incriminating statements scrawled inside the dry-docked boat where a wounded and bleeding Tsarnaev was

captured days after the tragedy.

“Stop killing our innocent people and we will stop,” he wrote.

Tsarnaev’s lawyers barely cross-examined the government’s witnesses and called just four people to the stand over less than two

days, all in an effort to portray the older brother as the guiding force in the plot.