Chad Fitzgerald described cell-site activity and its limits, while defense questioning distinguished recorded call durations from actual conversations. Witnesses described Sean Collier's shooting, emergency response, and surveillance; Nathan Harman identified the defendant beside the cruiser. The court also granted a jury view of the boat and restricted public display of autopsy photographs.
Full day summary
Sarah De Lair identified recovered backpack material, a pressure-cooker part, wire, and debris including BBs and nails. She described fragmentation as items that may have been used in the bomb. On cross-examination, she said she did not know whether the Q11 backpack had undergone fingerprint testing; its laboratory number established entry and photography, not which tests were performed.
FBI agent Chad Fitzgerald mapped calls between phones associated with the brothers around 2:49, 2:51, and 2:53 p.m. on April 15, along with later activity in Boston, Cambridge, and the New Bedford/Dartmouth area. He emphasized that cell sectors indicate general areas, not exact addresses, movement, or proximity between users. He agreed that the earlier calls were consistent with Jahar Tsarnaev being near the Forum and Tamerlan Tsarnaev near Marathon Sports, without pinpointing either. December 25–26 activity was consistent with possible use at 410 Norfolk Street, not an established location.
Defense questioning addressed Fitzgerald's preparation materials and the limits of call-duration records. He said network durations did not establish conversation time or whether anyone answered. He could not reconcile differing handset-extraction durations because he did not know how the software measured them. The court allowed Exhibits 1440 and 1485 as illustrative chalks while deferring admission. T-Mobile records were admitted as Defense Exhibit 2; the handset extraction and AT&T records were marked for identification, and the requested AT&T records were not admitted. On recross, Fitzgerald said his charts did not rely on the data-connection records that would reflect wireless calls.
FBI web manager James Eppard described the April 18 release of suspect images and video, subsequent updates, and extensive website traffic. He confirmed that the FBI video showed both suspects without emphasizing the white-hat individual. The prosecution withdrew a wanted-poster exhibit after a defense objection, while the court left an earlier admitted display's warning unredacted.
MIT and Cambridge witnesses described Sean Collier's final encounter with Chief John DiFava, unanswered dispatch calls, Sergeant Clarence Henniger's discovery of Collier shot in his cruiser, and emergency aid. DiFava demonstrated the holster's three retention protections. Henniger explained that the firearm remained holstered despite a lowered latch. Matthew Isgur authenticated surveillance showing two figures approaching the cruiser and returning along the same route, without identifying them. Nathan Harman identified the defendant as the man he saw leaning into the cruiser's open driver's door. He found a pictured sweatshirt consistent with his recollection but remembered different, knit-style headwear. The court directed that autopsy photographs be provided to jurors on paper rather than displayed publicly.
After the jury left, the court granted a view of the whole boat without commentary or evidence-taking and permitted removal of the message-bearing portion afterward. Location and timing remained under discussion, and press access was unresolved.