Video of a white Chicago officer shooting a black teenager 16 times shocked consciences around the world. Laquan McDonald was killed as he walked away from police.

Laquan McDonald killing: Chicago police officer sentenced to nearly seven years Read more

The graphic images of McDonald crumpling to the street while bullets kept striking him stirred expectations that the officer might pay a heavy price in prison time. The verdict came in October: a rare murder conviction for an officer in an on-duty shooting.

But on Friday a sentence of less than seven years for Jason Van Dyke – and the possibility that he may serve only half of that – led McDonald’s family and at least one activist to question whether justice had been done and the right message sent to other officers.

William Calloway, who was instrumental in the legal battle that led to the release of the dashcam video in 2015, described the penalty as “a slap in the face to us and a slap on the wrist” for Van Dyke.

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The sentencing came a day after a different judge acquitted three officers accused of lying about the shooting to protect Van Dyke, who was probably the first Chicago officer ever found guilty in the shooting of an African American. That verdict also disappointed many Chicagoans who hoped convictions would help eradicate a code-of-silence culture that dates back decades among officers in the nation’s third-largest city.

Van Dyke, 40, was convicted of second-degree murder and 16 counts of aggravated battery, one for each bullet fired at the 17-year-old McDonald. McDonald’s family lamented that the penalty was too light. His great-uncle said the sentence reduced McDonald’s life to that of “a second-class citizen” and “suggests to us that there are no laws on the books for a black man that a white man is bound to honor”.

In a brief statement, Van Dyke acknowledged the teen’s death, telling the judge that “as a God-fearing man and father, I will have to live with this the rest of my life”.

Prosecutors asked for 18 to 20 years. Defense attorneys argued that Van Dyke could be released on probation. The prison term was a fraction of what Van Dyke could have faced had he been convicted of first-degree murder, which carried a mandatory minimum of 45 years in prison.

Judges typically rebuke defendants during sentencings, even for much lesser crimes, and they often explain why they imposed the sentence they did. But Judge Vincent Gaughan did neither in his brief comments from the bench.

The lead defense attorney, Dan Herbert, said Van Dyke “truly felt great” after learning his sentence. “He was happy about the prospect of life ahead of him” and someday being reunited with his wife and two daughters. The prosecutor who oversaw the case said he can live with the sentence.

“Our goal was to find the truth, present the truth and ask for justice … It was not revenge,” special prosecutor Joseph McMahon said.

Had Gaughan sentenced Van Dyke on the 16 counts of aggravated battery, as prosecutors asked him to do, he could have faced decades in prison. Each aggravated battery count carried a mandatory minimum of six years, and the judge could have ordered those sentences to be served one after the other.

Facebook Twitter Pinterest The former Chicago police officer Jason Van Dyke. Photograph: Antonio Perez/AFP/Getty Images

The issue of race loomed over the case, although it was rarely raised at trial. One of the only instances was during opening statements, when the special prosecutor told jurors that Van Dyke saw “a black boy walking down the street” who had “the audacity to ignore the police”.

On Friday, several black motorists testified that the officer used a racial slur and excessive force during traffic stops in the years before the shooting. One of those witnesses, Vidale Joy, said Van Dyke used the slur after pulling him over in 2005 and at one point put a gun to Joy’s head. He said Van Dyke “looked infuriated” and seemed “out of his mind”.

Under cross examination, Joy acknowledged that he did not allege Van Dyke used a slur in his first accounts of the stop. Van Dyke’s relatives tried to defend and humanize him, saying he was a good father and not racist.

His wife, Tiffany, said her biggest fear was that somebody would kill her husband in prison “for something he did as a police officer, something he was trained to do”. She looked up over her shoulder and addressed the judge directly: “His life is over. Please, please. He has paid the price already ... I beg for the least amount of time.”

The video of the shooting triggered a federal investigation of the police department that found Chicago officers routinely used excessive force and violated people’s rights, particularly minorities.

The case cost Van Dyke and the Chicago police superintendent their jobs and was widely seen as the reason the county’s top prosecutor was voted out of office. It was also thought to be a major factor in Mayor Rahm Emanuel’s decision not to seek a third term.