"If I had a son, he would look like Trayvon," Obama said when he first addressed the case in March 2012. "When I think about this boy, I think about my own kids."
Despite White House efforts to carefully avoid weighing in on legal aspects of the case, Republicans have criticized the president for commenting at all, saying his words helped a local legal matter morph into a national spectacle.
"President Obama politicized this at the beginning of it, I believe, unfortunately, by injecting himself into it," said Karl Rove, former political adviser to President George W. Bush.
Rep. Steve King, R-Iowa, said the president turned a law-and-order matter "into a political issue." Rove and King both spoke Sunday on Fox News.
Zimmerman was acquitted Saturday in the February shooting death of Martin, who was unarmed when he was killed. Martin's parents and civil rights leaders said Zimmerman racially profiled the teenager when he followed him through a gated community and shot him, but Zimmerman said he was physically assaulted by Martin and shot the teenager in self-defense.
The Justice Department could still launch criminal civil rights charges against Zimmerman. Attorney General Eric Holder is reviewing evidence to determine whether to proceed on such charges after stepping aside to allow the state prosecution to run its course. However, legal experts say there are major hurdles to federal prosecution, including the burden of proving that Zimmerman, a former neighborhood watch leader, was motivated by racial animosity.
Holder, the nation's first black attorney general, said Monday that Martin's killing was a "tragic, unnecessary shooting." The Justice Department, he said, will follow "the facts and the law" as it reviews evidence to see whether federal criminal charges are warranted.
The NAACP and other civil rights organizations dismayed by the Florida jury's verdict are calling on the Justice Department to open a case against Zimmerman. As of Tuesday, more than 22,000 people had signed a White House petition supporting DOJ charges.
Senior White House officials have discussed the case with NAACP leaders in recent days, the organization said. But the White House insisted Monday that the president would not personally be involved in the decision to levy charges, nor would he weigh in personally on whether he supported that step.
"Cases are brought on the merits," Carney said. "The president expects, as in every case, that the process will be handled in the way it should be, at the Department of Justice, and certainly not here."