Prosecutors on Wednesday made their final appeal to the jurors who will decide the fate of Boston Marathon bomber Dzhokhar Tsarnaev, telling them that the young defendant had shown no remorse and that his actions "have earned him a sentence of death."

The jury was expected to begin its deliberations later in the day after hearing from Tsarnaev's attorneys and the judge.

Judge George O'Toole Jr. told jurors they have only two choices for punishing Tsarnaev: life in prison without the possibility of release or the death penalty.

"The choice between these very serious alternatives is yours and yours alone to make," the judge said.

"Merely killing the person isn't nearly as terrifying as shredding them apart."

- Prosecutor Steve Mellin

Prosecutor Steve Mellin said Tsarnaev wanted to cause his victims as much physical pain as possible to make a political statement.

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

"Merely killing the person," he said, "isn't nearly as terrifying as shredding them apart."

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 near where Tsarnaev placed his bomb. He showed another photo of bloodied victims on the sidewalk.

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

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

"He acted like it was any other day. He was stress-free and remorse-free," Mellin said. "He didn't care because the death and misery was what he sought that day."

During the four-month trial, prosecutors portrayed Tsarnaev as a callous, unrepentant terrorist who carried out the deadly attack with his radicalized older brother, Tamerlan.

Tsarnaev's lawyers admitted he participated, but told the jury he was "a good kid" who was led astray by Tamerlan, who wanted to punish the U.S. for its actions in Muslim countries. They have asked jurors to spare his life.

Mellin dismissed the contention that the older Tsarnaev somehow led his brother down the path to terrorism. "Tamerlan Tsarnaev was not the defendant's master. They were partners in crime and brothers in arms. Each had a role to play and each played it," he said.

Three people were killed and more than 260 injured when two bombs exploded near the marathon's finish line on April 15, 2013.

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 same jury must now decide his punishment.

In their opening statement in the penalty phase, Tsarnaev's lawyers urged the jury to sentence Tsarnaev to life in prison, calling it the most appropriate punishment for someone who was 19 when he committed the crime. They said a life sentence would also help the families of his victims, who would not be subjected to the years of appeals and public attention that would almost certainly follow a sentence of death.

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, living an austere, solitary existence until he dies and being denied the martyrdom he apparently sought.

Jurors must be unanimous in their decision to give Tsarnaev the death penalty. If even a single juror votes against death, Tsarnaev will be sentenced to life in prison.

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, in part because Tsarnaev expressed admiration for his brother, who he said died as a martyr.

"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."