Michael Slager now sits in jail as a convicted felon, much like the person who occupied his cell before him.

But unlike Dylann Roof, the mass killer whose death sentence was broadly expected, Slager's fate will remain a mystery until a judge decides it.

Much is riding on the result.

Some advocates, who point to the video of the former North Charleston patrolman shooting Walter Scott, want a stiff penalty that deters other police officers from using excessive force. But experts doubt that the prison sentence, lengthy or not, would do that.

Before Slager pleaded guilty last week to a federal civil rights violation, many in law enforcement already saw the shooting as egregious. For those officers, the experts said the case's outcome holds few lessons that could be applied to fatal confrontations that happen under more ambiguous circumstances: Eric Garner’s choking in New York, Freddie Gray’s rough ride in Baltimore and Alton Sterling’s shooting in Baton Rouge.

“Officers do what they are trained to do,” said Philip Stinson, a criminologist at Ohio’s Bowling Green State University who tracks police shootings nationwide. “This won’t change policing. It’s not going to send a message. They're going to continue to do what they do.”

Even Slager himself came to realize that he had gone too far when he fired eight times as Scott ran away, his attorney said. Facing state and federal prosecutions, he and his attorney knew the odds of dodging any conviction were long.

“It never was as simple as a traffic stop and a man shot in the back. There were complicating factors,” his lawyer, Andy Savage, said. “But the question became whether he should have recognized at some point that the man was running away.

“Even Slager now thinks it was excessive use of force.”

To some, his plea brought expressions of closure after a pair of racially charged episodes, including Roof's slayings of nine black church worshippers, have haunted the Charleston area for two years. But Slager's final chapter has yet to be written, and it still threatens to roil a community that has long struggled with race and justice.

The plea — hailed by activists as a civil rights victory — eliminated mandatory minimum sentences that a judge would be bound to impose.

It contains an element of risk for both sides, but few expect Slager to get the maximum lifetime penalty. Attorneys estimated that his sentence could fall between five and 20 years in prison.

The defense hopes a judge will agree that Slager's decision to fire the first shot was not criminal.

Authorities and Scott's loved ones, though, said the shooting is still murder and deserves a punishment that acts as a deterrent. The killing came during intense scrutiny of police uses of force, prompting inspection of tactics in North Charleston that residents long considered unfair.

"We need to shine a light on those cops, to let them know that you just can't get away with violating citizens," Scott's brother Anthony said last week. "It's no longer going to be tolerated, and you will be convicted if you do."

'Very concerned'

As the footage of Scott’s death surfaced and spread worldwide, Slager was arrested on a murder charge.

To his attorney, the case was winnable.

The situation became more difficult a year later. A federal grand jury indicted Slager on counts of depriving Scott of a right to be free from excessive force, using a firearm in a violent crime and lying to investigators.

The patrolman pulled over Scott’s car on April 4, 2015, for a broken brake light. The motorist ran, and the two fought. Saying he feared for his life when Scott grabbed his Taser, Slager fired and kept firing until Scott went down.

But the video showed Scott, 50, turning and running more than 10 feet away before the first of the eight shots went off. Five bullets hit him from behind.

Scott fell more than 50 feet away and died.

Before the federal charges were announced, prosecutors and defense attorneys discussed a plea bargain, sources familiar with their talks said. They couldn't strike a deal.

State prosecutors tried Slager first, but a jury couldn’t agree that he had committed murder, manslaughter or no crime at all. A mistrial was declared.

The focus shifted to U.S. District Court, where a jury would have been tasked with mulling whether the video showed excessive force.

"I was very concerned with that term, 'excessive force,'" Savage said. “At the time he decided to shoot, we don’t think it was criminal. But we’re not sure there was a threat when (Scott) was 22 feet, 28 feet, 31 feet away.”

A possible conviction on the firearms count, which comes with at least 10 years in prison, worried Slager.

He signed the plea deal that would drop the charge, along with the state’s murder case. In the same week his son turned 2 years old, it gave Slager hope of returning home during the boy’s childhood.

The move was hard for Slager's family to take. But it didn't shake his mother's belief that he had acted in self-defense from the first shot to the last.

A "police lives matter" pin affixed to her purse, Karen Sharpe said too many people have ignored the circumstances leading to the gunfire, such as evidence indicating Scott had tried to use the Taser against Slager. She hopes a judge will consider that.

"He's not evil; he's a very loving person," she said. "When you're in a situation he was in, nobody knows what they would do."

But she said her son "had to" plead guilty.

"It was Michael's decision," she said. "Whatever Michael's given, we will have to live with it."

Determining a sentence

Both sides of the story will approach its final chapter with apprehension.

A 600-page government manual eliminates only some of that uncertainty in federal sentencing. It ascribes numbers to circumstances of crimes, creating a formula for judges to consider.

“It used to be mandatory for the judge to pick a sentence in those guidelines,” said Mark Moore, an attorney at Nexsen Pruet in Columbia and former federal prosecutor. “But a court ruling said they had to be advisory.”

In Slager’s case, probation agents will crunch the numbers and send a report to Judge David Norton. Though Norton could pick any sentence, judges usually stick close to the guidelines.

Arguments during the sentencing hearing, which could come at least three months from now, will be crucial.

Norton must determine the underlying crime that Slager committed in violating Scott’s rights. Prosecutors will make a case for second-degree murder, which can carry about a 20-year sentence under the basic guidelines. The defense is expected to argue involuntary manslaughter, possibly bringing less than five years. A middle option, voluntary manslaughter, calls for around 10.

Other arguments could affect those numbers. The judge could weigh, for example, the unlikelihood that Slager would commit the crime again because his policing career is over.

'An aberration'

While Slager's guilty plea in federal court was rare for police killings, hefty penalties are less common, said Stinson, the criminologist.

He studied 32 civil rights prosecutions from 2005 to 2012, finding that 25 prompted convictions. Only six of those included plea deals.

But of the 28 murder cases that ended with some type of conviction, the average sentence for the officers was two years, Stinson said.

That's not the sort of penalty that would reform behavior among officers nationwide, observers said. Even if Slager's sentence breaks from that norm, the effect might prove minimal, they said.

“Officers can be very quick to distance themselves from bad acts, claiming this was rogue cop or a bad apple,” said Seth Stoughton, a law professor at the University of South Carolina and a former officer. “If they stick to the idea that this was an aberration … then you wouldn’t expect those officers to change."

Advocates have stressed other reform measures that are still being stressed locally, despite the federal governments' shift away from investigations into widespread civil rights abuses at police agencies nationwide.

Attorney General Jeff Sessions has disavowed such probes, but he said last week that officers will still be held accountable.

“Such failures of duty not only harm the individual victims of these crimes,” he said in a statement after Slager’s plea, “they harm our country, by eroding trust in law enforcement.”

The North Charleston Police Department has dealt with its own tangled history of strained ties with the community.

Chuck Wexler, executive director of the Washington, D.C.-based Police Executive Research Forum, had advised the force in past years on how to improve. He was devastated to see Scott’s shooting deal a blow to the effort.

But the sentencing and any federal oversight, he said, is not apt to change that. 

"What’s important is what the community expects," he said, “not what the federal government expects."

Shaundra Young Scott, executive director of the American Civil Liberties Union of South Carolina, echoed Wexler, saying the push in North Charleston, and other American cities struggling with the same problem, rests with those communities.

“Whatever the sentence is," she said, "Walter Scott’s shooting needs to be a catalyst for change so South Carolina can be an example and we can put this issue behind us.”

Reach Andrew Knapp at 843-937-5414 or twitter.com/offlede.

Andrew Knapp is editor of the Quick Response Team, which covers crime, courts and breaking news. He previously worked as a reporter and copy editor at Florida Today, Newsday and Bangor (Maine) Daily News. He enjoys golf, weather and fatherhood.