Police unions exist to advance the best interest of their members, even when officers are accused of wrongdoing.

But three weeks after an Illinois sheriff's deputy killed Sonya Massey in her own kitchen with a bullet to the face, Sean Grayson's guild went the other way − and experts say the move is significant.

The Illinois Fraternal Order of Police, a chapter of the largest national police union, announced in a rare move this week that it was dropping a grievance it had previously filed for Grayson, a former Sangamon County sheriff’s deputy who shot the 36-year-old-Black woman in her Woodside Township home after she called 911 to report a possible intruder. The deputy has since been fired and is being held without bail on murder charges, to which he pleaded not guilty.

The killing of Massey has sparked national outcry over police brutality, coast-to-coast demonstrations and a federal probe by the Justice Department.

Experts say the union's response to Massey's killing is rare, but it shows a growing attentiveness by police unions to public sentiment over police shootings and reflects the egregiousness of her death.

"Since 2020 and the murder of George Floyd, what we've seen is, simply put, more caution and less boldness, because there's recognition that there's been a shift in public perception of law enforcement," Michael Lansing, a professor of history at Augsburg University in Minneapolis who has studied the history of police unions, told USA TODAY.

Stories of justice and action across America. Subscribe to USA TODAY's This is America newsletter.

Evidence in Sonya Massey's killing led to outcry, union response

Shawn Roselieb of the Illinois Fraternal Order of Police Labor Council said the union initially represented the officer and tried to get him reinstated, actions that are standard union procedure.

"Our obligations under the collective bargaining agreement and to our members do not take away from the sympathy we feel for the family and loved ones of Sonya Massey,” Roselieb said in a statement shared with USA TODAY. “Our thoughts and prayers are with them and with all those impacted by this tragedy.”

It's "extremely rare" for a police union to drop a grievance so early on in the case, according to Jorge Camacho, policy director for the Justice Collaboratory at Yale Law School, and a clinical lecturer on policing and law.

He attributes the shift to the outraged community response to Massey’s killing and the mountain of evidence against Grayson, including body camera footage from the deputy next to him. It’s more common for unions to drop grievances after an officer is already convicted, since the law often requires that an officer convicted of a felony be fired, which would render a grievance moot, he said.

Body camera footage released by the department after the killing paints a shocking and gruesome picture. While Grayson barked at Massey to put down a pot of boiling water from another room, she ducked down and said "I'm sorry." He fired three shots at her, and the one that killed her entered below her left eye.

“You have to just ask why,” Camacho said. “Why is it that this one officer was so fearful for his life apparently, or at least so dismissive of the life of Sonia Massey, that he reacted with deadly force?”

Lansing said that body camera footage created a record of Grayson's actions "at the core of why the bargaining unit is backing away from supporting him."

The union did not immediately respond to additional requests for comment from USA TODAY.

The power of police unions

A police union traditionally backs its members accused of misconduct when they are facing disciplinary action. That became an established pattern in the 1970s and 80s, according to Lansing, the author of a forthcoming book about post-World War II policing in Minneapolis.

"Whenever there was a labor dispute, including over the actions of an officer and the use of deadly force, we saw police unions loudly, staunchly defending those individual officers facing some kind of discipline or punishment or even some type of civil lawsuit or criminal charges," he said.

Their obligation is to ensure the best economic interest of their members. For a member's conduct to be so egregious that it defies the union's own ethics and beliefs and prompts the union to abandon the member is "profoundly unusual," Lansing said.

Police unions largely derive their power from political and social influence, Camacho said, noting their “hard power” is actually quite limited. They are legally barred from striking, a defining capability of most unions, but they are viewed as the authoritative mouthpiece of police and public safety experts and wield great political power from relationships with government officials.

But there has been a shift to taking community sentiment into account, a concern that was historically reserved for police chiefs, mayors or other public officials who view themselves as being more directly accountable to the community. While it’s too early to say whether the Massey case will mark a new chapter in police union-community relations, Camacho said the starkly different response this week at least reflects a “heightened sensitivity” to public sentiment that has historically been lacking.

“I think now, police unions are realizing that if you lack public support, then you will lose politically in the long run and police unions are really sensitive to political losses,” Camacho said. “And I think that they feel that they've suffered a number of political losses over the years, and they're wary of inviting more political losses by fighting a disciplinary case that they ultimately view as unwinnable, or if it is winnable, it's for virtually no gain.”

Police unions are reacting more cautiously

Unions have become more politically savvy, Camacho said, and are paying more attention to addressing community grievances, especially since Floyd's murder. Lansing noted that police and police unions still have plenty of public support – take the popular "back the blue" sentiment and display of American flags with thin blue lines as proof – but unions are approaching deadly force cases with more "caution," he said.

In the Floyd case, the union that represented Derek Chauvin, who was convicted of murder, severed ties and condemned Chauvin's actions caught on video but denied that there was a larger problem of racism within policing, the Minnesota Reformer reported at the time.

The local union representing the officers who fatally shot Breonna Taylor in her own home, also in 2020, stood by the officers and later criticized a DOJ report that found Louisville police had violated the rights of citizens.

When former Huntsville police officer William Darby fatally shot a man after he called 911 six years ago, union leaders stood by his side. Officers in Alabama likely don’t fear the same repercussions from alleged misconduct that those in Illinois will, Camacho said. “So they have to play a different political game and engage in a different political calculus than officers elsewhere.”

Camacho predicts that some police unions at the local level will be “softening their tone,” especially in cases where misconduct is less contestable, political gain of fighting repercussions is minuscule and where officers “view themselves as politically vulnerable.”

But in cases where the evidence is less clear, perhaps when there is no body camera video to test the officer’s representations of what happened, Camacho said unions may feel less inclined to bow to public pressure and will stick to the officers' defense, even if misconduct is later proved.

Contributing: Michael Loria, USA TODAY; Steven Spearie, the Springfield State Journal-Register