Tamerlan and Dzhokhar Tsarnaev (Associated Press)

A comprehensive analysis of the weekday major network nightly newscasts delivers one unsurprising result: The top story of 2013 was the Boston Marathon bombings. ABC’s “World News” with Diane Sawyer devoted 119 minutes to the story; “CBS Evening News” with Scott Pelley, 157 minutes; and “NBC Nightly News” with Brian Williams, 156 minutes.

Far too much, in the opinion of the study’s pilot, longtime TV news watcher Andrew Tyndall. “All three newscasts overcovered the Story of the Year. The pressure-cooker bombs at the finish line of the Boston Marathon killed only three people. Yet emotional video from the scene and an all-out manhunt in a grieving city made up for the lack of carnage,” argued Tyndall in a summary of his report.

Come again? Didn’t this act terrorize the country? Didn’t it expose the continuing vulnerabilities of mass events? How could it have been overcovered? In a chat with the Erik Wemple Blog, Tyndall argued that because the bombing happened at such a well-documented and extensively videotaped event, and because so much drama followed it, the networks went overboard. “There were incidental reasons why it was a big story,” says Tyndall.

Those incidental reasons apparently convinced TV viewers across America that it was a big story, based on ratings spikes that boosted CNN and other news providers. The blanket coverage that television outlets devoted to Boston, says Tyndall, rendered them mute on a critical story that emerged in the midst of the chaos — namely, the Boston lockdown that took effect as authorities searched for the bombing suspects. “The fact that the news media overreacted in the same proportion as the police authorities did meant that they disqualified themselves” from criticizing the cops, argues Tyndall.

In addition to hammering the industry on Boston, Tyndall criticized ABC News’s nightly newscast for tamping down its coverage of major domestic and foreign-policy issues. More on that matter here and here.

Erik Wemple writes the Erik Wemple blog, where he reports and opines on media organizations of all sorts.