There was an extraordinary verdict in Chicago last week.

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There was an extraordinary verdict in Chicago last week. A white police officer was convicted of killing a black teenager. A Chicago police officer hasn’t been convicted of killing a suspect while on duty in more than a half century.

What might be even more extraordinary is that the police officer was charged at all. Jason Van Dyke was a 13-year veteran of the force. According to The Associated Press, he was the subject of at least 20 citizen complaints — eight of which alleged excessive force.

The killing occurred in 2014. Van Dyke shot 17-year-old Laquan McDonald 16 times as McDonald carried a knife and refused to heed the orders of police. The dash cam video of the incident is shocking and has been viewed by millions of people across the country.

The video is graphic and shows Van Dyke emptying his service pistol into McDonald as he fell and lay motionless on the ground. The video was concealed from the public for 13 months. Had the video remained under wraps Van Dyke might still be patrolling the streets of Chicago.

Even before the trial, the case had an impact on law enforcement in Chicago. The city’s police superintendent was fired and the county’s top prosecutor, who waited 400 days to file charges, lost a bid for reelection. The killing also led to a Department of Justice (DOJ) investigation.

Nicole Gonzalez Van Cleve, an Associate Professor at The University of Delaware, wrote in The Atlantic that the DOJ report detailed excessive use of force, including shooting unarmed citizens who did not pose a threat. The disciplining of officers was both rare and inconsistent. The report revealed that the Chicago Police Department engaged in coordinated efforts to “coach and conceal” misconduct.

A week before jury selection, Mayor Rahm Emanuel became the latest victim of the alleged cover-up, announcing he would not seek a third term. Emanuel faced fierce criticism after he fought the release of the dash cam video until after his re-election in 2015.

Prosecutors in Chicago charged Van Dyke with first-degree murder.

To find him guilty of first-degree murder, jurors had to find that Van Dyke “intended to kill or do great bodily harm to Laquan McDonald or he knew that such acts would cause death or he knew that such acts created a strong probability of death or great bodily harm” and he “was not justified in using the force which he used.”

Prosecutors had to prove his intent beyond a reasonable doubt — the highest standard of proof in the court system. Jurors clearly crossed that threshold, reported the Chicago Sun-Times. But the judge also instructed them to consider a “mitigating” factor.

Van Dyke’s lawyers had to prove that he, “at the time he performed the acts which caused the death of Laquan McDonald, believed the circumstances to be such that they justified (the) deadly force he used, but his belief that such circumstances existed was unreasonable.”

Van Dyke was convicted of second-degree murder and 16 counts of aggravated battery for each shot fired into McDonald. Following the verdict, three jurors said they had problems deciding between first and second-degree murder.

“Second-degree was the mitigating factor that in Mr. Van Dyke’s mind he was doing the right thing, he was experiencing an extreme threat, in his mind that’s how he’s experiencing it, and he felt like he needed to protect himself,” said one of the jurors.

This case is not over. Three other Chicago police officers — David March, Joseph Walsh and Thomas Gaffney — are charged with lying about the shooting and conspiring to protect Van Dyke from possible prosecution.

The three officers pleaded “not guilty” and are scheduled for trial beginning Nov. 26.

For some in Chicago, the next trial is as important as the last. Confidence in the police has eroded as a result of the alleged cover-up and the many cover-ups that created a 50-year lull in prosecuting police officers for using deadly excessive force.

— Matthew T. Mangino is of counsel with Luxenberg, Garbett, Kelly & George P.C. His book The Executioner’s Toll, 2010 was released by McFarland Publishing. You can reach him at www.mattmangino.com and follow him on Twitter @MatthewTMangino.