In this April 16, 2013 file photo, investigators examine the scene of the second bombing outside the Forum Restaurant on Boylston Street near the finish line of the 2013 Boston Marathon, a day after two blasts killed three and injured more than 260 people. During testimony Wednesday, March 11, 2015, in the federal death penalty trial of Dzhokhar Tsarnaev in Boston, an FBI agent held up pieces of the black and white backpack he said were found near the Forum restaurant, where Tsarnaev has admitted detonating one of the bombs.

Chief says he told MIT officer killed by bombers to be safe

John DiFava testified Wednesday about his last words to Collier in the federal death penalty trial of bomber Dzhokhar Tsarnaev.

In this April 20, 2013 file photo, investigators work near the boat in Watertown, Mass., where the previous night police captured Dzhokhar Tsarnaev, the surviving Boston Marathon bombing suspect, after a car chase and gun battle earlier in the day left his older brother dead. The prosecution presented as evidence Tuesday, March 10, 2015, during Tsarnaev's federal death penalty trial, photos of the handwritten note found inside the boat where he was captured four days after the bombings.

Jury in Boston bombing trial sees photos of writing in boat

Prosecutors consider the handwritten note a confession and say it refers to the motive for the attack carried out by Tsarnaev and his late b…