That prosecutor, Angela Corey, said her decision had no bearing on whether she would file charges against George Zimmerman, the neighborhood watch volunteer who has said he shot the unarmed black teen in self-defense. Corey could still decide to charge him with a serious felony such as manslaughter, which can carry a lengthy prison sentence if he is convicted.
A grand jury had been set to meet Tuesday in Sanford, about 20 miles northeast of Orlando.
Corey has long had a reputation for not using grand juries if it wasn't necessary. In Florida, only first-degree murder cases require the use of grand juries.
Corey's decision means she doesn't have to rely on potentially unpredictable jurors, said David Hill, an Orlando criminal defense attorney.
"Let's give her the benefit of the doubt. Maybe she knows there isn't enough for first-degree murder but she wants to maintain control and charge him with something else," Hill said. "What does she need a grand jury for? She cuts out the unpredictability of the grand jury. She goes where she feels she has more evidence."
Corey took over the case last month after the prosecutor who normally handles cases out of Sanford recused himself. That prosecutor, Norm Wolfinger, had originally called for the case to be presented before a grand jury.
"From the moment she was assigned, Ms. Corey noted she may not need a grand jury," said a statement from Corey's office.
Prosecutors sometimes use grand juries to avoid the political fallout from controversial cases. But Corey was elected by voters more than 100 miles away in the Jacksonville area, so political problems are less of an issue for Corey, Hill said.
Martin was killed Feb. 26 during a confrontation with Zimmerman in a gated community in Sanford.
Zimmerman has claimed self-defense, and Florida's self-defense law gives wide leeway to use deadly force and eliminates a person's duty to retreat in the face of danger.
Zimmerman's attorney, Craig Sonner, said he didn't want to comment on Corey's decision.
An attorney for Martin's parents said in a statement that he is not surprised by the decision to avoid the grand jury and hopes a decision is reached soon.
"The family has been patient throughout this process and asks that those who support them do the same during this very important investigation," said attorney Benjamin Crump.
The case has led to protests across the nation and spurred a debate about race and the laws of self-defense. Martin was black; Zimmerman's father is white and his mother is Hispanic.
In Georgia, a civil rights activist is challenging that state's so-called stand your ground law. The Rev. Markel Hutchins said he sued Monday in Atlanta in response to Martin's death. The lawsuit claims the law leads to the unnecessary use of lethal force.
On Monday, one protest led to the temporary closing of the Sanford Police Department offices to the public for most of the day as about a half dozen student activists blocked the building entrance.
Police officers took no action to remove the protesters, who were part of a group of students who marched from Daytona Beach to Sanford over the weekend.
Citizens wanting to do business with the police department were directed to City Hall.
Calling themselves "the Dream Defenders," the protesters demanded Zimmerman's arrest; a special investigation into the Sanford Police Department; a community meeting; and the firing of the city manager and the police chief who temporarily stepped down after Martin's death, Bill Lee. Darren Scott, a 23-year veteran of the Sanford Police Department, was named acting chief. Lee is still employed with the department and receiving his salary.
After meeting with six of the protesters, city officials agreed only to a community forum next week.
"The city certainly is committed to justice for Trayvon Martin," said City Manager Norton Bonaparte Jr.
