Boston bomber Dzhokhar Tsarnaev is a remorseless terrorist who deserves to die for killing innocent Americans, prosecutors told jurors Wednesday as they prepared to deliberate whether or not he should be sentenced to death.

The defense hit back that he was a "lost kid," from a rootless and troubled family, ignored by his parents, manipulated by his radicalized older brother and who had expressed genuine remorse to a Catholic nun.

Convicted Boston bomber Dzhokhar Tsarnaev has expressed sincere remorse for carrying out the deadly attacks in 2013, a prominent American nun and anti-death penalty campaigner told his trial Monday.

Sister Helen Prejean, who was portrayed in an Oscar-winning performance by actress Susan Sarandon in Hollywood movie "Dead Man Walking," was the final witness called by the defense in its bid to save Tsarnaev from death.

Convicted Boston bomber Dzhokhar Tsarnaev for the first time showed some emotion in court on Monday, wiping his eyes as a distraught aunt was removed from the courtroom, too overcome to testify.

A jury is mulling whether Tsarnaev -- found guilty last month of all counts related to the April 15, 2013 attack on the Boston Marathon that killed three people and wounded 264 more -- should be sentenced to death or life in prison without parole.

Thousands of people demonstrated in major U.S. East Coast cities Wednesday demanding equal treatment for all by police, after a young African American died of injuries sustained in custody in Baltimore.

The biggest show of people power was in Baltimore itself -- epicenter of the latest racially tinged unrest to convulse the United States -- where several thousand mostly young demonstrators paralyzed city blocks in a major rally through downtown to City Hall.

A crack defense team launched its bid Monday to save Boston bomber Dzhokhar Tsarnaev from the death penalty, blaming his older brother Tamerlan, "consumed by jihad," for the 2013 carnage.

"As awful as his crime was, life in prison faced with what he has done is a better choice for everyone," said lawyer David Bruck in his opening statement at the penalty phase of Tsarnaev's trial.

Prime Minister Shinzo Abe visited Washington's Holocaust Memorial on Monday to hail a rare hero of Japan's brutal World War II past.

Previously, Abe has faced criticism for his allegedly revisionist views of Japan's own war-time behavior.

Relatives of the policeman shot dead after the Boston bombings gave harrowing testimony Wednesday as the defense downplayed a new video of convicted killer Dzhokhar Tsarnaev flipping his middle finger.

The 21-year-old former university student will be sentenced either to death, or to life in prison without parole, by a jury after the second phase of his trial, now under way.

Boston bomber Dzhokhar Tsarnaev is "America's worst nightmare" and deserves to die for one of the bloodiest attacks on U.S. soil since 9/11, his trial heard Tuesday.

The court was shown a never-before seen photograph of Tsarnaev, dressed in an orange prison jumpsuit flipping his middle finger at a surveillance camera in a cell before his first arraignment.

Convicted Boston Marathon bomber Dzhokhar Tsarnaev must face death for the attack that killed three people and wounded 254, prosecutors will argue when a court this week begins weighing up his fate. 

The sentencing phase of Tsarnaev's high-profile trial begins Tuesday in the city, just days after the parents of a young boy killed in the dual blasts on April 15, 2013 asked for the death penalty to be dropped.

The sentencing phase of the Boston bombings trial, which will condemn convicted killer Dzhokhar Tsarnaev to death or life imprisonment, will begin on April 21, the judge ruled Friday.

It will come the day after the city holds the 2015 edition of its popular marathon, which Tsarnaev and his elder brother Tamerlan attacked with twin pressure-cooker bombs on April 15, 2013.