The storyline quickly took root, amplified by the nearly ubiquitous images of the two: a sweet-looking photo of a several-years-younger Trayvon released by his family, and a mug shot of Zimmerman from a previous arrest in which he looks puffy and downcast. The contrasting images powerfully reinforced the images of the menacing bully and the innocent victim.

Some of the media’s major mistakes stemmed from stories that fit neatly into that widely accepted narrative. NBC News edited Zimmerman’s comments during a phone call to inaccurately suggest that he volunteered that Trayvon seemed suspicious because he was black. In fact, Zimmerman was responding to a question when he mentioned the teenager’s race. The network apologized for the error.

Similarly, ABC News broadcast a story reporting that a police surveillance video showed no evidence that Zimmerman suffered abrasions or bled during the confrontation with Trayvon. Shortly thereafter, it “clarified” the situation, reporting that an enhanced version of the video showed Zimmerman with “an injury to the back of his head.” …

A healthy dose of skepticism should always be part of the journalism process. And in this case there was a particularly strong reason for caution. While some residents of the complex saw some parts of the conflict, only two people knew, really knew, how it went down. And one of them was dead. Under those circumstances, certainty was elusive.