Calls for police reform have spread across the United States, but after years of acting with relative impunity -- supported by powerful unions and protective laws -- changing the worst habits of the US men in blue will be a steep challenge.
After the May 25 death of George Floyd, the African-American who died while handcuffed and pinned to the ground at the neck by a white Minneapolis police officer, communities, states and even Congress have piled up initiatives to stem police violence, especially against blacks.
In Minneapolis, the city council has called for a wholesale dismantling and rebuilding of the Midwestern city's police department.
In other communities, critics are demanding to "defund the police" -- to force budget reductions and reappropriations that would bring about change.
And in Congress, Democrats proposed nationwide reforms that would lower the legal threshold for police to face prosecution, including charges for use of excessive force.
"This movement of national anguish is being transformed into a movement of national action," said House Democratic leader Nancy Pelosi.
Pattern of abuse
Floyd's death was just the latest incident in a larger pattern of police use of lethal force.
US police killed 1,098 people in 2019, one-quarter of them black Americans, who represent only 13 percent of the population, according to the group Mapping Police Violence.
By comparison, French police kill only around 20 people every year.
One explanation for the huge US number is the widespread availability of guns, which increase the danger faced by officers on the job.
Last year, 135 officers were killed in the line of duty, according to the National Law Enforcement Officers Memorial Fund.
US police are empowered to use their firearms at any "reasonable" expectation of immediate danger to themselves or others -- a subjective standard.
Given the somewhat wide parameters at issue, the cases of police being charged with excessive or flagrant abuse are extremely rare.
Police are also protected by the contracts their unions negotiate, which make it much more difficult to pursue them in court, according to the activist group Checkthepolice.org, which has compiled details on such contracts in more than 80 cities.
The Minneapolis contract allowed Derek Chauvin, who held his knee to Floyd's neck for nearly nine minutes, to keep his job for almost two decades despite 18 reports of abuse.
Reluctant prosecutors, juries
Over the past 15 years, just 110 police have been charged with felony homicide after killing someone while on duty, and only five have been convicted of murder, according to Philip Stinson, a former police officer who is now a professor of criminal justice at Bowling Green State University in Ohio.
"Prosecutors are reluctant to bring charges because they have to work with police officers for their day-to-day work," Stinson said.
And it is hard to win a case against a cop because juries are "very reluctant" to second-guess a policeman's split-second decision to shoot in a dangerous situation, he added.
On top of that, said Minnesota law professor David Schultz, jurors do not trust many of those who accuse the police of abuse.
The accusers "are oftentimes not... the most sympathetic people," he said.
Theoretically, a victim of police abuse could sue in federal court.
But getting a favorable judgment against the police is almost impossible, thanks to Supreme Court rulings that grant officers a "qualified immunity" for doing their jobs.
To win, a victim would have to prove the police violated a "clearly established law."
In practice, this allows police to wiggle out of situations that have never been specifically tested in court.
For example, a man who sued over being bitten by a police dog as he sat on the ground lost his case, because the only precedent that had been set was for someone bitten while lying on the ground.
18,000 autonomous entities
While the "qualified immunity" issue could soon again be tested in the Supreme Court, more than 200 members of Congress have proposed legislation to lower the threshold for charging police with using excessive force.
They also want more race sensitivity training for police and to create a registry for officers sanctioned for abuse.
But the challenge is dealing with 18,000 autonomous police departments across the country -- towns, counties, cities, and states all have their own forces, recruitment parameters, training practices and specific rules.
After several notorious unjustified police shootings, former president Barack Obama launched federal investigations into 25 police departments, including in Baltimore and Ferguson, Missouri.
Some of those achieved local changes but did not address the problems on a national scale. Since President Donald Trump took office in 2017, there have been no such investigations.