Just before a jury began deliberating the fate of Boston Marathon bomber Dzhokhar Tsarnaev, prosecutors reminded jurors of the pain and suffering caused by the bombing and said Tsarnaev deserves to die for what he did.

But Tsarnaev's lawyer said he was an "invisible" teenager in a dysfunctional family who was led astray by his older, radicalized brother and deserves a chance at redemption.

The federal jury of seven women and five men began deliberating late Wednesday after listening to powerful closing statements from prosecutors and Tsarnaev's lawyers. Jurors will return to U.S. District Court on Thursday to resume deliberations.

Prosecutor Steve Mellin told the jury that Tsarnaev is a callous "remorse-free" terrorist who bombed the marathon with his brother, Tamerlan, to make a political statement against the U.S. for its wars in Muslim countries.

Three people were killed and more than 260 were injured when two pressure-cooker bombers packed with shrapnel exploded near the marathon finish line on April 15, 2013.

Mellin said Tsarnaev wanted to cause his victims as much physical pain as possible.

"The bombs burned their skin, shattered their bones and ripped their flesh," Mellin said. The blasts "disfigured their bodies, twisted their limbs and punched gaping holes into their legs and torsos."

Defense attorney Judy Clarke asked jurors to spare Tsarnaev's life, saying her client "is not the worst of the worst, and that's what the death penalty is reserved for."

"We think that we have shown you that it's not only possible, but probable that Dzhokhar has potential for redemption," she said, adding that he was "genuinely sorry for what he's done."

The prosecutor showed a large photograph of 8-year-old Martin Richard, who was killed in the attack, and other children standing on a metal barricade. Tsarnaev placed his bomb just 3½ feet from the children. Another photo showed bloodied victims on the sidewalk.

"This is what terrorism looks like," Mellin said.

Tsarnaev, he said, showed no regret after the bombings, calmly going to buy a half gallon of milk 20 minutes later.

From the beginning of the trial, Tsarnaev's lawyers admitted he participated in the bombing, but told the jury he was "a good kid" who was led down the path to terrorism by Tamerlan.

Clarke said Tsarnaev's parents favored his older brother and pinned their hopes on him, believing he would become an Olympic boxer. She showed photos of his father at boxing matches with Tamerlan, and then asked, "Where are the pictures of Dzhokhar? He was the invisible kid."

The Tsarnaevs, who are ethnic Chechens, lived in the former Soviet republic of Kyrgyzstan and the volatile Dagestan region of Russia, near Chechnya, before moving to the U.S. about a decade before the bombings.

Tamerlan was a "jihadi wannabe" who returned to the U.S. angry and frustrated after an unsuccessful attempt to join Islamic extremists in Russia, Clarke said. Then he decided to find another way to wage jihad.

"If not for Tamerlan, this wouldn't have happened. Dzhokhar would never have done this, but for Tamerlan. The tragedy would never have occurred but for Tamerlan — none of it," Clarke said.

Mellin said the two brothers were "partners in crime and brothers in arms."

Tsarnaev, 21, was convicted by a federal jury last month of all 30 counts against him, including use of a weapon of mass destruction.

The defense showed the jury photos of the federal Supermax prison in Florence, Colorado, where Tsarnaev would probably be sent if he gets life. There, his lawyers said, he would be locked in his cell 23 hours a day — a solitary existence that would deny him the martyrdom he apparently sought.

A sentence of life "reflects justice and mercy," Clarke said.

Mellin reminded jurors that some of them — before they were chosen for the jury — expressed a belief that a life sentence may be worse than death.

"This defendant does not want to die. You know that because he had many opportunities to die on the streets of Boston and Watertown. But unlike his brother, he made a different choice," Mellin said.

"A death sentence is not giving him what he wants. It is giving him what he deserves."