(CNN) As a Minnesota jury found former Minneapolis police officer Derek Chauvin guilty of murder and manslaughter charges, law enforcement experts note how rare it is that police officers involved in high-profile, and sometimes deadly, on-duty incidents ever face criminal charges or are convicted.
Experts point to several factors, which include laws that protect an officer's right to use force, advantages from powerful police unions, prosecutors who may face a conflict of interest, and even jury pools that tend to side with police.
"It's rare because the juries are very reluctant to second guess and judge the actions of on-duty police officers in violent street encounters," said Philip Matthew Stinson, a criminal justice professor at Bowling Green State University who spearheads a group that tracks data on police crimes.
Stinson, who collects and tracks data from news reports and court records across the country with his team at the Henry A. Wallace Police Crime Database, started tracking in 2005. In that time, the team's data has revealed that at least 140 law enforcement officers have been arrested on murder or manslaughter charges related to on-duty shootings in the US.
From that pool, about a third were convicted on any charges. Seven officers -- just 5% -- have been convicted of murder during that same time frame, according to their research. Because the researchers' data is based on cases that are reported in the media, it may not be comprehensive or representative, but it captures a snapshot that suggests how rare charges for these offenses may be.
The current standard for police use of force is the 1989 US Supreme Court decision that says force must be "objectively reasonable," and reasons that officers are "often forced to make split-second judgments -- in circumstances that are tense, uncertain and rapidly evolving -- about the amount of force that is necessary in a particular situation."
The standard, which is under the federal constitution, influenced some state legislatures to interpret their constitutions similarly, and many individual police agencies have incorporated that federal standard into their own policies and training, according to Brandon Garrett, professor of law at Duke University School of Law and faculty director of the school's Wilson Center for Science and Justice.
"These cases are never in nice, neat packages. The facts are always bad for both sides," Stinson says about most cases involving police officers. "There are facts here that favor the defense, and there are facts here that favor the prosecution. Neither of them has a case that's in an absolute certainty to the extent you could have something like that in a jury trial."
There is no reliable data set that tracks on-duty shootings dating back to 2005. But according to The Washington Post's police shootings database, on-duty police officers have shot and killed more than 5,000 people since 2015. Data on the number of incidents in which police officers use deadly force is also lacking.
Police officers who stand trial for murder or manslaughter have a unique set of advantages that make a criminal conviction less likely, according to Garrett.
"In this country, many uses of force are not crimes, criminal charges are rare, and we've seen grand juries decline to indict in high-profile cases," said Garrett. "Unlike the vast bulk of criminal cases that result in convictions through guilty pleas, many police officers do not plead guilty and they are successful in trial."
In the past few weeks, there have been several high-profile instances of police killings that exemplify how police use of deadly force is "far more common than it should be in this country," Garrett said.
In recent weeks, body-worn camera footage showed then-police officer Kim Potter fatally shoot 20-year-old Daunte Wright during a routine traffic stop in a Minneapolis suburb last week and separately, a Chicago police officer making a split-second decision to fire a single shot that killed 13-year-old Adam Toledo in late March and video from last May of Chauvin kneeling on George Floyd's neck was aired again and again.
Former Brooklyn Center, Minnesota police chief Tim Gannon said Potter, who was charged with second-degree manslaughter in Wright's death, mistook her gun for her Taser. In Chicago, Toledo was shot after he was seen holding what police said was a handgun at the end of a foot chase down a dark alley. The boy is seen raising his hands at the same time the officer fires his weapon, according to police body camera footage.
In many states, attorneys for police officers argue that their use of force and conduct was justified under "split-second circumstances," which refers to rapidly evolving police encounters, according to Garrett.
Police defendants often turn down plea offers knowing that their defense will likely succeed at trial. Officers often secure defense attorneys just hours after the incident occurs and they have high-quality union representation from the onset to advise on their strategy, experts say.
"The quality of the lawyering is very different from regular criminal cases," Garrett added. "For the typical criminal defendant, it's incredibly risky to go to trial."
In 2018, prosecutors charged East Pittsburgh police officer Michael Rosfeld with criminal homicide in the fatal shooting of 17-year-old Antwon Rose II. Rosfeld, who is White, was found not guilty on all charges the following year. Rose, an unarmed Black teenager, was shot in the back while running away during a traffic stop.
Patrick Thomassey, the defense attorney for Rosfeld, told CNN this week that juries in criminal trials involving police are often torn because they know officers are authorized by law to use deadly force when they are confronted with it.
"People on the outside don't understand what the law is. There are training and use of force statutes determining when police can use deadly force," Thomassey said. "You have to look at whether he had a right to use it at the time he used it."
And it is more than not understanding the scope of the law. Police defendants also benefit from juror sympathy due to the public perception that their job is inherently dangerous, which can broaden their range of self-defense arguments.
"Officers know that they have legal defenses that wouldn't otherwise be available because they have a professional role in which they are authorized to use force that no one else is," Garrett said. "That makes for a very different case."
On the same day that the jury cleared Rosfeld of all charges, seven bullets were fired into Thomassey's law office in Monroeville, Pittsburgh, he said.
"There's always so much emotion involved in these cases," Thomassey said. "That's the hard part from a defense posture and a prosecution posture. You just hope that the people listen to the law, set aside whatever emotions are involved, follow the law, and render the proper decision."
Chauvin's actions spurred law enforcement officials to violate the so-called "blue wall of silence" with no one's testimony shining a bigger spotlight than that of the Minneapolis police chief, saying that the former officer violated department policy and the use of force was unjustified.
The near-unprecedented departure from the unwritten code shows both how some police officials condemn Chauvin's actions and how unique the trial has become.
Chief Medaria Arradondo testified that Chauvin should have stopped kneeling on George Floyd's neck when he stopped resisting and became nonresponsive, saying Chauvin was wrong to "apply that level of force to a person proned out, handcuffed behind their back."
In past cases, the "blue wall of silence" provides cover around an officer accused of using deadly force, inhibiting cops from speaking out against others in their police department, according to Garrett.
"Hopefully that will set a precedent that agencies will not stand by the worst conduct of their officers," he said. "If jurors aren't sure what police officers are or are not supposed to do, they may see the police front is reflecting that the person's conduct must have been appropriate police behavior."
Garrett said there are hundreds of instances where police use deadly force each year but despite the fatality, very few of those incidents result in an officer facing criminal charges.
In the aftermath of Chauvin's guilty verdict, Garrett believes there will continue to be a "rethinking" of how and when officers should be held civilly and criminally liable when they cause a death. The problem is that there is very little data available on deadly force used by police.
In police brutality cases, the question is whether the officer accused of misconduct acted "reasonably" and their behavior was necessary under the circumstances -- but how "reasonable" is defined remains largely elusive.
"There are so few cases that tell us what reasonable is, and that's why a conviction in the Derek Chauvin trial would set a standard for reasonable that we didn't have before," said Gloria Browne-Marshall, professor of constitutional law at John Jay College of Criminal Justice and civil rights attorney.
The Chauvin trial is a rare example of "zealous prosecution" in hundreds of years where prosecutors have failed to prosecute White people for crimes against Black people, Browne-Marshall said.
Despite viral images of police using what some argue to be excessive force, most are deemed reasonable by prosecutors and grand juries, whether because the officer's actions found to be justified or there is not enough evidence to file criminal charges.
Sam Aguiar, one of the attorneys representing the family of Breonna Taylor, said he's all too familiar with the sting a family feels when police aren't charged, and prosecutors could have done more.
Taylor was a 26-year-old emergency medical technician when she was shot and killed by Louisville police officers in her apartment during an early-morning raid in March 2020. A grand jury indicted only one of the officers on three counts of wanton endangerment, as prosecutors said he blindly fired 10 shots into the home. That officer pleaded not guilty.
Aguiar said the difference between his case and the Chauvin trial is that Minnesota state prosecutors aren't being asked to go after police officers they work with every day.
"These prosecutors use a cost-benefit analysis and it's: do we go after a police officer for what is criminal conduct and really diligently pursue the case and get a conviction and take the risk of losing the support of our key witnesses on hundreds of other cases, or do we basically sack the case," Aguiar said. "When you bring in an independent body to come in and basically put all the resources into holding the officer accountable, that you're actually going to get a situation where a trial is put together that really does present all the evidence objectively."
And not to be understated, police departments around the country spoke out against Chauvin's actions, with no bigger example of that than Arradondo, taking the stand against Chauvin, one of his former officers. It's something, Aguiar says, he hopes to see in other cases moving forward.