The Memphis police enacted reform measures in 2020.

In 2020, the city of Memphis voted to require the Memphis Police Department to enact policies designed to reduce the use of excessive force by officers. The measures came in the wake of the high-profile killings of George Floyd and Breonna Taylor by law enforcement officers.

The department eliminated the use of no-knock warrants. Officers were required to use de-escalation strategies and intervene if they saw others using excessive force, in accordance with 8 Can’t Wait, a nationwide campaign to limit the use of force by police. They could shoot at a suspect only as a last resort and had to attempt to issue a verbal warning beforehand. And each time they used, or threatened to use, force against civilians, they had to report it. A ban against chokeholds was already in place, officials said in 2020.

“I understand the frustrations that our citizens are feeling, and I realize the importance of transparency and accountability as we reform law enforcement nationwide,” Michael Rallings, then the director of the Memphis Police Department, said in the summer of 2020, announcing reform measures.

But the death of Tyre Nichols after a confrontation with five police officers, who have since been fired, shows that the work of reforming the department continues, said Van Turner, a lawyer and president of the Memphis branch of the N.A.A.C.P.

“We need to find ways to better implement policies and training which are already on the books,” said Mr. Turner, who served on the Shelby County Board of Commissioners, the county’s legislative body, until last year and advocated for many of the police reforms enacted in 2020.

The majority of the Memphis Police Department is Black, according to data published on a city website. Of nearly 2,000 commissioned officers, about 58 percent are Black, 37 percent are white and 3 percent are Hispanic.

In recent years, as Memphis grappled with a spike in violent crime, local attention drifted away from police reforms, Mr. Turner said.

In 2021, the city recorded a record number of murders, with 346, and the violent crime rate only marginally improved last year. The killings have stirred fear among residents and spurred calls to bolster the ranks of the department.

“We’re tired of the break-ins, the carjackings, the assaults,” Mr. Turner said. “And so there was more support for law enforcement in the communities.” But he said Mr. Nichols’s death would renew focus on reform. “This takes it back up,” he said.

The department has drawn scrutiny over accusations of officer misconduct before. In 2021, William Skelton, a former Memphis police officer, was charged with official oppression involving the repeated pepper-spraying of a 28-year-old man while he was handcuffed. He has pleaded not guilty.

In 2015, a man was stopped by a plainclothes police detective who had been following him in an unmarked car. The man, Daniel Jefferson Jr., said he did not realize the man following him was an officer and shot him in self-defense, according to an account by Mr. Jefferson that was in a report by internal investigators. Mr. Jefferson said that three other officers then took him into custody and beat him with table tennis paddles and a chair, according to the report. The officers denied the allegations. They were suspended without pay and criminal charges were never brought.