The federal inquiry into Mr. Garner’s death dragged on for years and has divided the Justice Department investigative team since the Obama administration. Prosecutors in New York argued against bringing charges, while civil rights prosecutors in Washington said it represented a clear case of excessive force. In the final months of the administration, the attorney general at the time, Loretta E. Lynch, sided with her civil rights chief, Vanita Gupta, and authorized prosecutors to build a case for indictment.
Mr. Garner’s mother, Gwen Carr, said on Friday that Justice Department officials had promised to tell her when a decision was made. “I haven’t heard anything,” she said. “I’m hopeful. But we’ll never know until there’s a decision.”
The fate of the investigation has been uncertain under the Trump administration. Mr. Sessions has rolled back efforts to use his civil rights team to investigate unconstitutional police practices and force changes on entire departments. He said that approach, favored by the Obama administration, unfairly tarnished good police officers and contributed to racial unrest.
But Mr. Sessions has also promised to hold officers accountable for abuses. “Just as I am committed to defending law enforcement who use deadly force while lawfully engaged in their work, I will also hold any officer responsible breaking the law,” he told the National Organization of Black Law Enforcement Executives last year.
Mr. Trump’s pick to lead the civil rights unit, Eric S. Dreiband, has been awaiting a vote in the Senate for months. John M. Gore, a deputy chief and a Trump appointee, is temporarily overseeing the division. Career prosecutors specializing in police abuse have been running the Garner investigation.
Devin O’Malley, a Justice Department spokesman, had no comment.
“It’s been a long road for Officer Pantaleo and a very frustrating one,” said Stuart London, Mr. Pantaleo’s lawyer. “He has always been confident that he never violated Eric Garner’s civil rights. He’s also always denied he used a chokehold.”
“Any time there is a loss of life, it’s a tragedy,” he said, adding, ”It’s been a long road for the Garner family, too.”
It is rare for civil rights prosecutors to recommend criminal charges against officers in excessive force cases. Declining to indict would be certain to ignite fresh criticism that the Justice Department under Mr. Sessions is indifferent to allegations of police abuse.
But law enforcement officials, including some on both sides of this case, acknowledge serious challenges with the case. When he was attorney general, Eric H. Holder Jr. said the evidence clearly justified indictment, but he acknowledged prosecutors might lose at trial.
Ms. Lynch was less certain and deliberated for months before allowing it to move forward. Even some of the civil rights prosecutors who argued in favor of charging Officer Pantaleo acknowledged that the case had weaknesses. For instance, some former officials said the initial F.B.I. team believed early on that Officer Pantaleo had done nothing wrong and skewed their investigation accordingly.
A state grand jury previously declined to bring charges in the case.
Police abuse cases are among the most difficult courtroom challenges that prosecutors face. Juries frequently give great deference to police officers for actions carried out under pressure. That is important because, before bringing charges, federal prosecutors must consider whether they are likely to win at trial — a rule that some civil rights advocates say gives officers an advantage before charges are even filed.
Officer Pantaleo has said he did not mean to put Mr. Garner in a chokehold. The officer said he tried to use a “seatbelt maneuver,” which involved hooking an arm underneath one of Mr. Garner’s arms while wrapping the other around his torso. During the struggle, Officer Pantaleo said he feared he would be pushed through a storefront window behind him.
Federal prosecutors in Brooklyn were convinced by that argument, but the civil rights specialists were not. They said the video, captured by a bystander, showed clear evidence of willful wrongdoing. In particular, they have singled out the moments after Officer Pantaleo was clear of the storefront window and appeared to keep putting pressure on Mr. Garner’s neck.
The spate of high-profile deaths at the hands of police officers spurred angry, sometimes violent protests around the country, inspiring changes in policing strategies in many cities and a federal push to collect better data on the use of force.
Officer Pantaleo has been on desk duty since shortly after Mr. Garner’s death. While the police department’s internal inquiry of him has been completed, the results are unknown and police officials are waiting to mete out any potential discipline — up to and including termination — until the federal government resolves its own case.