NEW YORK >> On the first anniversary of her husband’s death, Esaw Garner lit a candle and said a silent prayer. She assumed that closure would be coming — one way or another. After all, federal officials had personally assured her that they would reinvestigate the New York City police officer who had put her spouse, Eric Garner, in a chokehold in the moments before he died.

But now, the second anniversary is approaching, and although Esaw Garner will light another candle and say another prayer when she observes it July 17, the inquiry that buoyed her hopes has continued unresolved. She is sick of the waiting and tired of the worrying. What she wants most is simply to move on.

“I miss my husband dearly, but I’ve basically stopped asking them what’s going on,” Esaw Garner said in an interview last week. “If they’re going to do something, then they’ll do it. But it’s in God’s hands now. I’m done.”

Killings involving police officers seemed to have occurred in recent years with a striking regularity, including two last week: one on July 5 in Baton Rouge, La., and a second in a suburb of St. Paul, Minn., on Wednesday night. While the federal government does not investigate a majority of these episodes, when it does get involved — as it announced it would in the Louisiana case — the inquiries can often be protracted.

The long delays in the Garner investigation, which has been especially closely watched, have come about for several reasons: There are inherent complexities in the federal civil rights law and a desire among officials to move with caution in a delicate matter. But there has also been, according to those involved, a heated disagreement over how — and even whether — to go forward. Prosecutors with the U.S. attorney’s office in Brooklyn, whose jurisdiction also extends to Staten Island, Queens and Long Island, have expressed doubts that they can prove in court that a crime had been committed; their counterparts in Washington have claimed that they are confident they have sufficient evidence to proceed.

The dispute came to a head at a recent meeting in Washington, where both offices offered their opinions to Attorney General Loretta E. Lynch. Lynch, formerly the top U.S. prosecutor in Brooklyn, must now decide between siding with her former colleagues or with the special civil rights team that investigates such cases. It is unclear both what and when she will decide.

“It is taking quite a bit of time,” said William Yeomans, a fellow at the American University School of Law, who once served as the acting assistant attorney general for civil rights. “I’d almost say it’s been longer than expected, especially since a video exists.”

That video, which, by now, has been viewed around the world, showed Eric Garner, 43, struggling in the grasp of Officer Daniel Pantaleo, who was trying to arrest him on suspicion of selling loose cigarettes on a Staten Island street in July 2014. Five months later, a state grand jury declined to bring charges against Pantaleo, touching off a wave of protests in New York and a national debate about policing in minority communities.

As they have in other local cases that have failed to go to trial, a team of federal prosecutors opened their own investigation, convening a grand jury that has been sitting intermittently in Brooklyn since February. Experts and officials say that the outcome of the case will hinge on whether Pantaleo purposefully deprived Garner of his civil rights.

“Here’s the challenge,” said Alan Vinegrad, a former federal prosecutor from Brooklyn. “You have a split-second decision by a police officer on the street in the exercise of his official duties. It’s extremely difficult to say what is and isn’t a willful violation of someone’s civil rights.”

These challenges have, in fact, set off a vigorous debate between prosecutors in Washington and Brooklyn. Lawyers in the Justice Department’s civil rights division believe they have enough evidence to prove that Pantaleo acted willfully. But some with the U.S. attorney’s office have been hesitant; according to three current and former federal law enforcement officials, the Brooklyn prosecutors went so far as to argue against taking the case to a grand jury in the first place.

While prosecutors in Washington have developed a reputation in the past several years for aggressively investigating systemic police misconduct in cities like Chicago, Baltimore and Ferguson, Mo., they and their counterparts in U.S. attorney’s offices across the country have been more reluctant to charge individual officers with using deadly force. The last time the federal government brought a deadly force case against an officer in New York was in 1998, when Francis X. Livoti stood trial on — and was eventually convicted of — charges of choking to death a young Bronx man named Anthony Baez.

In most investigations of police abuse, Yeomans said, prosecutors try to get officers to testify against their peers by confronting them with misleading incident reports or with the officers’ own contradictory witness statements.

“But in this case,” Yeomans added, “it’s all about parsing the video, probably frame by frame. It may be hard, but how long can it take?”

Federal investigators have indeed broken the video down, frame by frame, for prosecutors to interpret.

Lynch, who was the first U.S. attorney promoted directly to attorney general in nearly 200 years, has a reputation for being deferential to prosecutors in the field rather than micromanaging them from Washington. But on policing matters, she has also relied heavily on the advice of her civil rights prosecutors, who are more removed from the local police departments they investigate.

In the meantime, Pantaleo remains on desk duty and may face charges from within the police department, if the federal grand jury fails to indict him or if the prosecutors decide to drop their case.

As for Esaw Garner, hope has been replaced by deep frustration.

“I was a lot more optimistic last year,” she said. “This year, I don’t know. They keep telling me that no stone will be left unturned. But how much investigation do you need?”

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