The notorious Boston bomber Dzhokhar Tsarnaev has been found guilty of using a weapon of mass-destruction during the 2013 marathon.
Three people were killed and 264 injured on 15 April 2013, when the 21-year-old and his older brother Tamerlan Tsarnaev, carried out the attacks. They planted two home-made shrapnel-packed pressure cooker bombs near the finishing line of the marathon. Two women, 23-year-old Lingzi Lu and 29-year-old Krystle Campbell, and eight-year-old Martin Richard were killed by the explosions.
After the bombings, the two brothers then sought to evade the police and went on the run. They shot an MIT police officer following a gun battle with Watertown police and Tamerlan was killed when he was run over by his brother.
Jurors took nearly 12 hours over the course of two days to reach their verdict, convicting Dzhokhar who faces 30 federal charges in connection with the bomb attack. The jury viewed video taken by security cameras near the finish line on Boylston Street showing defendant Dzhokhar Tsarnaev and his brother at the scene of the blasts.
Surveillance video and images show the defendant walking with a backpack that prosecutors contend held a bomb, leaving it in a crowd in front of a restaurant, making a brief phone call and walking away shortly before the blast.
The guilty verdict was read out in the U.S. District Court in Boston, in the presence of relatives of the victims and survivors of the deadly attacks, one week ahead of the second anniversary of the bombing.
With 17 of the charges carrying the death penalty, the guilty verdict means Dzhokhar is eligible for the death penalty.
While his attorneys acknowledged that he carried out the attacks along with Tamerlan, the defence attempted to convince jurors that Tsarnaev was pressured by his radicalised brother who masterminded the bombings.
In the hope that Dzhokhar might be spared the death penalty, the defence attorney Judy Clarke said: "If not for Tamerlan, it would not have happened."
However, prosecutors contended that Dzhokhar, an ethnic Chechen, had read and listened to jihadist materials ahead of the murders and had deliberately targeted men, women and children at the marathon to terrorize the US and avenge the deaths of fellow Muslims overseas.
Following the gun battle, Dzhokhar was found hiding from police in a boat. He had written a note inside the vessel suggesting the bombing was an act of retribution for U.S. military campaigns in Muslim-dominated countries.
On Monday, Assistant U.S. Attorney Aloke Chakravarty told the jury that Tsarnaev had intentionally chosen to carry out the "cold, calculated" attack.
"He chose a day when there would be civilians on the sidewalks. He and his brother targeted those civilians, men, woman and children, because he wanted to make a point. This was a cold, calculated terrorist act. This was intentional. It was bloodthirsty. It was to make a point. It was to tell America that we will not be terrorized by you anymore. We will terrorize you."
"He wanted to punish America for what it was doing to his people. That day they felt they were soldiers, they were mujahideen, and they were bringing their battle to Boston," the prosecutor added.
A second phase of the trial will now begin, during which additional testimony will be heard before the jury determines whether to sentence Dzhokhar to death or life in prison.