Weeks before the 2013 Boston Marathon, Dzhokhar Tsarnaev and his older brother went to a New Hampshire firing range for shooting practice. In a form, Tsarnaev listed his experience with a handgun as “intermediate,” and for $170.75 the brothers spent an hour with a Glock 17 and a Glock 34, shooting through four boxes of ammunition.
Prosecutors say the brothers used their practiced skills to kill an MIT police officer days after the April 15, 2013, bombing, and again when they shot at police in Watertown.
For much of the day Tuesday, prosecutors in Tsarnaev’s federal death penalty trial focused on his familiarity with a gun, and the mayhem caused by the firefight with police in Watertown as the brothers sought to flee. At least 256 rounds were fired in a residential neighborhood. One bullet pierced the wall of a nearby house and entered a room, and an MBTA police officer was struck — possibly by crossfire — and nearly died.
Jurors also heard from an FBI agent who detailed the evidence discovered in Tsarnaev’s dorm room, including a box of BBs, a receipt for a Smith & Wesson replica BB gun, and the white hat prosecutors say Tsarnaev was wearing the day of the Marathon bombings.
While defense attorneys have named Tsarnaev’s older brother, Tamerlan Tsarnaev, as the gunman, prosecutors have sought to show that the younger brother was a willing participant all along, well familiar with the use of a firearm.
Tsarnaev, now 21, has admitted through his lawyer that he and his brother set off the bombs at the Marathon finish line that killed three people and injured more than 260 others. Tamerlan Tsarnaev was killed during the confrontation with police in Watertown, after he was shot several times and then run over by his younger brother.
With prosecutors seeking a death sentence, lawyers for Dzhokhar Tsarnaev have sought to use the trial to show that his older brother was the mastermind of the attacks carried out in the name of jihad, or Muslim holy war, against the United States.
They say the younger Tsarnaev was pressured into taking part in the bombing, and that his life should be spared.
To that end, defense lawyers used a State Police crime scene investigator’s testimony to show that Tamerlan Tsarnaev’s fingerprints were found on a Ruger 9mm pistol that was found on Laurel Street in Watertown, the scene of the shootout, as well as on a magazine of ammunition.
Dzhokhar Tsarnaev’s were not.
Also, according to previous testimony, Tamerlan Tsarnaev was the one who fired at police officers during the confrontation with authorities in Watertown.
But prosecutors sought to use testimony Tuesday to place Dzhokhar Tsarnaev by his side.
They pointed to the BB gun that was also found at the Watertown scene, the same Smith & Wesson model listed on the receipt in the defendant’s dorm room. It was found not far from the Ruger pistol.
Authorities ultimately determined that 56 of the 256 discharged cartridge cases that investigators found on Laurel Street in Watertown came from the Ruger 9mm pistol. The same weapon was also used to kill MIT police Officer Sean Collier, testified State Police Lieutenant David Cahill, who specializes in firearms identification.
One of Dzhokhar Tsarnaev’s friend’s, Stephen Silva, testified earlier in the trial that the Ruger was the same gun he loaned to Tsarnaev two months before the Marathon bombing.
Miguel Colon, a Watertown police officer, testified Tuesday that he saw Tsarnaev flee the Watertown shootout in a Mercedes-Benz, after his older brother was tackled by police officers.
Tsarnaev hit his brother with the SUV, dragging him down the road.
Tsarnaev’s lawyers have pointed out that the Mercedes was sprayed with bullets to suggest that MBTA police Officer Richard Donohue was hit in the crossfire.
Also Tuesday, a counterterrorism and intelligence analyst who testified as a prosecution witness acknowledged while being questioned by defense attorney David Bruck that Islamic radicals are usually influenced by something, whether it is a person or propaganda.
Bruck suggested that Tamerlan Tsarnaev radicalized his younger brother.
Bruck has also suggested that Dzhokhar Tsarnaev was vulnerable to manipulation because of personal and family issues after the summer of 2012. Tsarnaev began failing his college classes that fall, during his second year. And according to one witness Tuesday, Tsarnaev had appealed to the college to continue his financial aid, saying in a letter, “This year I lost too many of my loved relatives. I was unable to cope with the stress and maintain school work.”
In the letter, which did not include any specifics about the relatives he said were falsely accused, Tsarnaev said the distractions had come to an end and he was ready to turn his full attention to his academic pursuits.
A year earlier, Tsarnaev’s parents had divorced and both left the country for Dagestan, where they had lived before emigrating to the United States.
Tsarnaev returned from his first year in college to the family home on Norfolk Street in Cambridge, now occupied only by his older brother, his wife, and their toddler daughter.
The analyst Matthew Levitt, who had testified a day earlier for prosecutors, said that Dzhokhar Tsarnaev by then had a collection of jihadi propaganda on his computer and other electronic devices.
“At some point, it doesn’t make a difference where you got them from, if you got them and internalized them,” Levitt said.
Over 12 days of testimony, jurors have heard from 80 witnesses, and prosecutors this week could finish presenting their case in the first phase of the trial.
It’s unknown whether the defense will present any witnesses.
Milton J. Valencia can be reached at mvalencia@globe.com. Follow him on Twitter @miltonvalencia.