In the past two years, the Justice Department has issued statements to announce and explain the lack of federal charges after investigations into the fatal shooting of Trayvon Martin in Sanford, Fla.; the death of a teenager whose body was found in a rolled-up gym mat in a Georgia high school; and the use of force by a white sheriff’s deputy, who flipped a black female student out of her chair and threw her across a high school classroom floor in South Carolina.

On occasion, the authorities have gone even further, calling conduct into question even when the actions were not prosecutable.

Perhaps the most notable example occurred last year, when the director of the F.B.I., James B. Comey, announced that the bureau was closing an investigation into the handling of classified information by Hillary Clinton, the Democratic presidential candidate. Although the bureau found no evidence that Ms. Clinton or her colleagues had intended to violate the law, Mr. Comey said, there was evidence that they had been “extremely careless.”

Mr. Comey acknowledged that his statement was “unusual” and that he was including “more detail about our process than I ordinarily would, because I think the American people deserve those details in a case of intense public interest.”

The fact that prosecutors and investigators are speaking more freely has fueled debate among legal experts over whether the authorities, when closing their investigations without filing charges, should issue such comments.