Key Moments Day 14 Of Tsarnaev Trial Testimony: How The Bombs Were Built

Testimony in the trial of admitted Boston Marathon bomber Dzhokhar Tsarnaev on Thursday focused on how the bombs used on Boylston Street and in Watertown were built.

Below find four key moments from Thursday's testimony, and see all of Thursday's live coverage here.

-An FBI chemical forensic examiner, David McCollam, testified Thursday about explosives — specifically how to obtain enough black powder to create a sizable explosion.

What was not answered Thursday is exactly how the Tsarnaev brothers obtained enough black powder to fill three pressure cooker bombs (later established to hold at least 8 pounds of powder), several pipe bombs, and a plastic container found filled with 2 to 3 pounds of powder.

-FBI Supervisory Special Agent Edward Knapp is member of TEDAC — the Terrorist Explosive Device Analytical Center. He and his team were charged with piecing the Boylston Street and Watertown bombs back together.

The ignition device, Knapp testified, was a single light from a string of Christmas tree lights with the filament exposed to light explosive material.

-Knapp later read through an Inspire Magazine (a publication of al-Qaeda) article on how to build homemade pipe and pressure cooker bombs. The article details many techniques used in the Boylston Street and Watertown bombs, including attaching BBs to the sides of the containers and using a Christmas light as the ignition.

-This is how the prosecution will end its case: by presenting to jurors grisly autopsy photos of the three killed in the marathon bombings while medical examiners who conducted their autopsies explain their injuries. Prosecutors are expected to rest on Monday.


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Jack Lepiarz Reporter and Anchor
Jack Lepiarz was a reporter and anchor at WBUR.



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