The Response

Since the unrest in Ferguson, Mo., in 2014 amid a rising debate over how police treat black people, police departments around the country have responded to demonstrations calling for greater police reform and accountability. In St. Louis, only miles from Ferguson, state and city officials had braced for large-scale protests after the acquittal of the former police officer, Jason Stockley, in the death of Anthony Lamar Smith, a 24-year-old black man. So far, the police have reported at least a dozen injuries to law enforcement officers, but no life-threatening injuries to either officers or protesters.

“They’ve done a sound job of finding that inflection point and not letting that boisterousness cross over into rioting.”

— David A. Klinger, professor of criminology and criminal justice at the University of Missouri-St. Louis and a former Los Angeles police officer “Police should have some type of distance, allow them to do what they need to do. Let them protest. Let them get their message out. Let them chant. Stay away from them. All they’re supposed to be there to do is to give some oversight.”

— Ja’Mal Green, an activist in Chicago

But the police drew criticism on social media on Monday when, according to The St. Louis Post-Dispatch, officers were heard chanting “Whose streets? Our streets,” a common protest refrain. Schron Y. Jackson, a spokeswoman for the St. Louis police, said department officials were reviewing a video that appeared to show the chant. “We hold our officers to the highest standards of professionalism, and any officer not meeting those standards will be held accountable,” she said in an email.

“The police by their very nature should be and ought to be neutral parties, and statements like the ones made could be seen as taking sides. It’s better to discuss the lawless actions of a few. That’s what the focus should be on.”

— Ronal Serpas, former police chief of New Orleans and Nashville, now a professor at Loyola University New Orleans

The Arrests

After some people threw rocks into windows and at officers and toppled planters downtown, arrests were essential, the experts said, especially once officers gave clear orders for the increasingly volatile crowd to disperse.

“It appears from the news reports that generally they have done a good job in trying to move the rioters out of the area and keep them from doing certain things.”

— Jim Bueermann,a former Redlands, Calif. police chief who is now president of the Police Foundation, a nonpartisan research group.

Swept up in the arrests late Sunday and early Monday was a journalist, Mike Faulk, a reporter for the St. Louis Post Dispatch. Mr. Faulk wrote on Twitter that while covering the protests, he had become trapped with a group of about 100 people and could not follow police orders to leave. In a photo of his arrest, Mr. Faulk’s press credentials were hanging visibly around his neck.

“The police’s work is to facilitate the peaceful protest and to try to find a way to contain the small element that will commit criminal acts. But they have to understand that that’s not most of the protesters. When they do these sweeps in which people, including reporters and legal observers, are arrested, that’s not effective policing.”

— Paul Butler, law professor at Georgetown University and former federal prosecutor

The Leadership

In an early morning news conference on Monday, Chief O’Toole, who has been the acting chief since April, praised the officers on his force, and said that the police were “in control,” adding: “I’m proud to tell you the City of St. Louis is safe, and the police owned tonight.”