Fury over her killing by the police in Louisville, Ky., fueled protests, and questions persist about how the botched raid unfolded.

The death of Breonna Taylor, a Black medical worker who was shot and killed by police officers in Louisville, Ky., in March 2020 during a botched raid on her apartment, was one of the main drivers of wide-scale demonstrations that erupted that year over policing and racial injustice in the United States.

No officer has ever been charged with shooting Ms. Taylor, but on Aug. 4, 2022, the Justice Department charged four current and former police officers with federal civil rights violations, including lying to obtain a search warrant for her apartment.

One of the four, Kelly Goodlett, a detective who retired after getting charged, pleaded guilty at a hearing on Aug. 23. Another officer among the four, Kyle Meany, was fired by the Louisville Police Department on Aug. 19.

A third officer facing the federal charges, Brett Hankison, was the only officer to face state charges in the raid, but a jury found him not guilty in March 2022. He had been charged with endangering Ms. Taylor’s neighbors after firing 10 bullets through a covered window and sliding glass door. Some bullets passed through Ms. Taylor’s apartment and into a neighboring one where a family had been sleeping.

On Nov. 16, a jury deadlocked on the federal charges against Mr. Hankison, leading to a mistrial. He had been charged with violating the rights of Ms. Taylor and her neighbors by firing the shots through the window and glass door. It was not immediately clear, following the mistrial, whether the Justice Department planned to retry the case.

A New York Times examination of video footage from the scene, witness accounts, statements by the police officers and forensics reports showed that the raid was compromised by poor planning and reckless execution. It found that the only support for a grand jury’s conclusion that the officers had announced themselves before bursting into Ms. Taylor’s apartment — beyond the assertions of the officers themselves — was the account of a single witness who had given inconsistent statements.

Ms. Taylor’s family has long pleaded for justice, and her case began to draw national attention in May 2020. Later that year, Louisville officials agreed to pay $12 million to settle a wrongful-death lawsuit brought by Ms. Taylor’s mother and to institute reforms aimed at preventing deaths by officers. In December 2022, a lawyer for Ms. Taylor’s boyfriend, Kenneth Walker, said that the city of Louisville had agreed to pay $2 million to settle lawsuits brought by Mr. Walker.

Following national demonstrations in 2020 over police brutality and systemic racism, Louisville officials banned the use of no-knock warrants, which allow the police to forcibly enter people’s homes to search them without warning, and fired several officers, including Mr. Hankison, who was found to have shown “an extreme indifference to the value of human life.”

Still, critics say progress in the case has been slow, especially when compared with the police killing of George Floyd in Minneapolis, where officers were swiftly fired and charged.

“At this point it’s bigger than Breonna, it’s bigger than just Black Lives,” Ms. Taylor’s mother, Tamika Palmer, said over the summer of 2020 as she beseeched the authorities to bring criminal charges. “We’ve got to figure out how to fix the city, how to heal from here.”

Shortly after midnight on March 13, Louisville police officers executing a search warrant used a battering ram to enter the apartment of Ms. Taylor, a 26-year-old emergency room technician.

The police had been investigating two men who they believed were selling drugs out of a house that was far from Ms. Taylor’s home. But a judge had also signed a warrant allowing the police to search Ms. Taylor’s residence because the police said they believed that one of the men had used her apartment to receive packages. Ms. Taylor had been dating that man on and off for several years but had recently severed ties with him, according to her family’s lawyer.

Ms. Taylor and her boyfriend, Mr. Walker, had been in bed but got up when they heard a loud banging at the door. Mr. Walker said he and Ms. Taylor both called out, asking who was at the door. Mr. Walker later told the police he feared it was Ms. Taylor’s ex-boyfriend trying to break in.

After the police broke the door off its hinges, Mr. Walker fired his gun once, striking Sgt. Jonathan Mattingly in a thigh. The police responded by firing several shots, striking Ms. Taylor five times. Mr. Hankison shot 10 rounds blindly into the apartment.

Mr. Walker told investigators that Ms. Taylor coughed and struggled to breathe for at least five minutes after she was shot, according to The Louisville Courier Journal. An ambulance on standby outside the apartment had been told to leave about an hour before the raid, counter to standard practice. As officers called an ambulance back to the scene and struggled to render aid to their colleague, Ms. Taylor was not given any medical attention.

It was not until 12:47 a.m., about five minutes after the shooting, that emergency personnel realized she was seriously wounded, after her boyfriend called 911.

The Jefferson County coroner told The Courier Journal that Ms. Taylor most likely died less than a minute after she was shot and could not have been saved.

Jamarcus Glover, Ms. Taylor’s ex-boyfriend whose alleged packages led the police to her door that night, was arrested on Aug. 27, 2020, in possession of drugs, according to a charging document. He told The Courier Journal that Ms. Taylor had no involvement in the drug trade.

No drugs were found in Ms. Taylor’s apartment, a lawyer for Mr. Walker said.

“Breonna was a woman who was figuring everything out in her life, who had turned a corner,” said Sam Aguiar, a lawyer representing Ms. Taylor’s family. “Breonna was starting to live her best life.”

Breonna Taylor, 26, was killed on March 13, 2020 by officers executing a so-called no-knock warrant.Family of Breonna Taylor, via Agence France-Presse — Getty Images

The Louisville police say that they fired inside Ms. Taylor’s home only after they were first fired upon by Mr. Walker, Ms. Taylor’s boyfriend. Mr. Walker was subsequently charged with attempted murder of a police officer, though the charge was dismissed in May 2020.

While the department had received court approval for a “no-knock” entry, the orders were changed before the raid to “knock and announce,” meaning that the police had to identify themselves.

The police assert that they knocked several times and identified themselves as police officers with a warrant before entering the apartment. Mr. Walker has said he and Ms. Taylor heard aggressive banging at the door and asked who it was, but they did not hear an announcement that it was the police.

The police said that the officers “forced entry into the exterior door and were immediately met with gunfire.” Three officers returned fire, the police said.

Several of the officers involved in the raid — Mr. Hankison, Detective Myles Cosgrove, and Detective Joshua Jaynes — were fired. Another officer, Mr. Mattingly, retired from the force.

Yes, hotly. Ms. Taylor’s relatives and their lawyers say that the police never identified themselves before entering — despite their claims. They also say that Mr. Walker was licensed to carry a gun.

And Mr. Walker, 27, has said that he feared for his life and fired in self-defense, believing that someone was trying to break into the home.

The police’s incident report contained multiple errors. It listed Ms. Taylor’s injuries as “none,” even though she had been shot several times, and indicated that officers had not forced their way into the apartment — though they used a battering ram to break the door open. There was no body camera footage from the raid.

On Aug. 4, prosecutors said that three officers — Joshua Jaynes, Kelly Goodlett and Kyle Meany — made false claims in an affidavit used to obtain the warrant and conspired to lie about it after.

The affidavit claimed that Ms. Taylor’s ex-boyfriend had been receiving packages at her address, but prosecutors say that there was no such evidence and that the officers misrepresented the case to the judge who signed off on the raid.

Mr. Jaynes sent a draft of the affidavit to Ms. Goodlett, who prosecutors said knew the claim was false but further bolstered it with “misleading” information. Mr. Meany, who led a department investigative unit, approved the affidavit despite knowing that it contained false information.

Two months after Ms. Taylor’s death, Mr. Jaynes and Ms. Goodlett met and agreed to falsely tell investigators that a sergeant had told them that the packages were being sent to Ms. Taylor’s apartment, prosecutors said.

Ms. Taylor’s family has disputed the police’s claim that the raid had to be conducted in the middle of the night. Their lawyers say the police had already located the main suspect in the investigation by the time they burst into the apartment. But they “then proceeded to spray gunfire into the residence with a total disregard for the value of human life,” according to a wrongful-death lawsuit filed by Ms. Taylor’s mother.

The Justice Department accused Mr. Jaynes and Mr. Meany of violating Ms. Taylor’s right to be free from unreasonable searches and seizures. Ms. Goodlett and Mr. Jaynes were accused of conspiring to falsify the affidavit; Ms. Goodlett was also accused of conspiring to hinder the subsequent investigation.

Mr. Hankison was accused of depriving Ms. Taylor, her boyfriend and their neighbors of their rights by unreasonably firing 10 bullets through a window and sliding glass door that were covered with blinds.

City officials banned the use of no-knock warrants on June 11, 2020. About a year later, Gov. Andy Beshear signed Senate Bill 4 into law, a bipartisan bill that partially bans no-knock warrants.

Greg Fischer, who was mayor at the time, announced other changes to ensure “more scrutiny, transparency and accountability,” including the naming of a new police chief; a new requirement that body cameras always be worn during the execution of search warrants; and the establishment of a civilian review board for police disciplinary matters.

The Breonna Taylor case prompted the Justice Department to conduct a wide-ranging investigation of the Louisville Metro Police Department, and the agency released the results on March 8, 2023, in a damning 90-page report. Investigators detailed a pattern of serious abuses, including excessive force; searches based on no-knock warrants; car stops, detentions and harassment of people during street sweeps; and broad patterns of discrimination against Black people and people with behavioral health problems.

Local officials said the report accurately reflected the complaints of citizens for years, and vowed to restore trust in the department.

Along with the findings, Attorney General Merrick Garland and Mayor Craig Greenberg, who took office in January, announced an agreement to overhaul policing in Louisville. “We will not make excuses,” the mayor said. “We will make changes.”

Christina Morales, Christine Hauser Will Wright, Sarah Mervosh, Lucy Tompkins, Glenn Thrush, Giulia McDonnell Nieto del Rio, Neil Vigdor, Jenny Gross and Rukmini Callimachi contributed reporting.