The jury in the Boston Marathon bombing trial on Wednesday saw two unexploded pipe bombs that prosecutors contend Dzhokhar Tsarnaev hurled at police officers during a gunfight on a dark suburban street four days after the bombings.
The call "we need the bomb squad" came over Massachusetts State Trooper Robert McCarthy's radio early on April 19, 2013, after Tsarnaev and his 26-year-old brother, Tamerlan, began tossing homemade devices at police, McCarthy testified.
Dzhokhar Tsarnaev, 21, is charged with killing three people and injuring 264 with a pair of homemade bombs at the race's crowded finish line on April 15, 2013, and with fatally shooting a university police officer three days later.
During the gunfight, hours after the Tsarnaevs are accused of fatally shooting the officer, the pair threw one bomb of the same apparent design as the pressure-cooker devices they set off at the race, prior witnesses have testified. Witnesses described that bomb as temporarily blurring their vision and shaking houses.
McCarthy also described how investigators used robots to pick up the two unexploded pipe bombs from the scene of the shootout, which shattered the calm of a street lined with homes.
The unexploded metal bombs shown in court were filled with explosive powder and lined with metal pellets used in BB guns, said McCarthy, adding that one was an "improvised grenade" designed to explode where it landed, without rolling.
Tsarnaev's lawyers opened the trial early this month by saying they largely accepted prosecutors' account of the defendants' actions but left in place his "not guilty" plea, leaving it to the federal government to prove its case.
Defense lawyers are seeking to portray Tamerlan as the driving force behind the attacks, arguing that Dzhokhar followed him out of a sense of subservience. Proving that point could persuade the jury to sentence the younger brother to life in prison without possibility of parole, rather than death.
The elder Tsarnaev died after the gunfight. Dzhokhar briefly escaped and was found hiding in a boat after a daylong lockdown of much of the greater Boston area.
Stephen Silva, a high school friend of Tsarnaev's who federal prosecutors contend loaned Tsarnaev the gun used in the shooting, testified under cross examination on Wednesday that Tsarnaev did not want him to meet Tamerlan, whom Silva said Tsarnaev described as "very strict, very opinionated."
Tsarnaev left a note in the boat that suggested the attack was an act of retribution for U.S. military campaigns in Muslim-dominated countries.
The bombing killed restaurant manager Krystle Campbell, 29, graduate student Lingzi Lu, 23, and 8-year-old Martin Richard.
Massachusetts Institute of Technology police officer Sean Collier, 27, was shot dead three days later.