US prosecutors have rested their case against Boston Marathon bombing suspect Dzhokhar Tsarnaev after jurors in his trial saw gruesome autopsy photos and heard a medical examiner describe the devastating injuries suffered by the three people who died in the 2013 attack.

Prosecutors finished their case on Monday and Tsarnaev's lawyers will now get a chance to present theirs.

Three people were killed and more than 260 were injured when two pressure-cooker bombs, allegedly set up by Tsarnaev and his older brother Tamerlan, exploded near the marathon's finish line on April 15, 2013.

Prosecutors have presented testimony from survivors who lost legs in the bombings and from the father of eight-year-old Martin Richard, the youngest person killed in the explosions.

Tsarnaev's lawyers did not cross-examine any of the victims but instead focused on trying to show that his brother was more culpable in the attack and in the killing three days later of Massachusetts Institute of Technology police officer Sean Collier.

Prosecutors believe the brothers were seeking retaliation against the US for wars in Muslim countries.

The defence has made it clear since testimony began on March 4 that its strategy during the two-phase trial is not to win an acquittal for Tsarnaev, but to save him from the death penalty.

Once the defence case is complete, jurors will deliberate on whether Tsarnaev is guilty of the 30 federal charges against him in the bombing, in Collier's killing and for his role in a violent confrontation with police.

Tamerlan Tsarnaev, 26, was killed during the confrontation, both by gunshots and from being run over by Dzhokhar as he escaped.

Dzhokhar Tsarnaev was found more than 18 hours later hiding in a boat parked in a yard.

Second phase

If the jury convicts Tsarnaev - an event that may be a foregone conclusion because of his admitted guilt - the trial will move on to the second phase, when the same jury will hear more evidence to decide whether Tsarnaev should be put to death or should spend the rest of his life in prison.

During this second phase of the trial, Tsarnaev's lawyers will present evidence of factors they believe mitigate his crimes, such as his age at the time - 19 - and the influence of his older brother.

The Tsarnaevs - ethnic Chechens - lived in the former Soviet republic of Kyrgyzstan and the volatile Dagestan region of Russia before moving to the US with their parents and two sisters about a decade before the bombings. 

Source: Agencies