Thomas Grilk

Thomas Grilk testified for the prosecution on Day 27 about the Boston Marathon's crowded finish area and the organizers' response to the bombings. As executive director of the Boston Athletic Association and finish-line announcer, he explained the race's scale, logistics and spectator crowds. His testimony supplied context for the setting and aftermath rather than identifying a perpetrator or addressing the brothers' respective roles.

During direct examination, Grilk authenticated four photographs and a photo-bridge video, admitted as Exhibits 1 through 5. He explained the video clock and agreed that its reading corresponded to approximately 2:49 p.m. During playback, he identified Marathon Sports near one blast and the Forum restaurant near the second. He also described efforts to assist approximately 5,600 stopped runners, recover their belongings and treat injured people. He testified that everyone who entered the medical tent alive remained alive.

The diagrams used during his testimony became the focus of cross-examination. The defense accepted their use as chalks but objected to admission; the court deferred admission and marked them for identification. Under Miriam Conrad's questioning, Grilk acknowledged that he had not prepared the diagrams or taken measurements. Their scale looked about right to him based on walking along the street, but he could not confirm that every depicted business was present in 2013 or identify certain small brown features. The government declined further questioning, and Grilk was excused.