(CNN) - Prosecutors in Illinois are challenging the sentence of former Chicago police officer Jason Van Dyke, who killed a black teenager in 2014, sparking protests, a federal civil rights investigation and the eventual ouster of the police superintendent.
A jury convicted Van Dyke last fall of second-degree murder and 16 counts of aggravated battery with a firearm. In January, Cook County Judge Vincent Gaughan sentenced him to six years and nine months in prison on the murder charge for killing Laquan McDonald. Van Dyke fired 16 shots in about 15 seconds.
The aggravated battery charges carried potentially more prison time. Each of the 16 counts would have carried a minimum sentence of six years in prison. When combined, Van Dyke could have faced up to 96 years in prison, a stiff penalty many protesters and activists were hoping for.
Illinois Attorney General Kwame Raoul and Kane County State's Attorney Joe McMahon, the special prosecutor who tried the case, filed a petition -- called a writ of mandamus -- in the Illinois Supreme Court asking the court to vacate Van Dyke's second-degree murder sentence, authorities said. The petition asked to instead impose a sentence on each of the 16 counts of aggravated battery with a firearm.
They are also asking the court to determine which of those aggravated battery convictions "involved 'severe bodily injury' warranting consecutive sentences."
Authorities said they plan to work with the court to review the legality of the sentence.
"It is important that a police officer was held accountable for criminal conduct," McMahon said in the statement.
"But we argued at the sentencing hearing that Jason Van Dyke should be sentenced for the aggravated battery with a firearm convictions. The ability for the prosecution to challenge a sentence is very narrow, but this might be one of those situations," he said.
If the court accepts the petition, Van Dyke's attorneys will generally have seven days to file an objection.
Van Dyke was originally charged with first-degree murder, but jurors were instructed they could also consider the second-degree murder charge.
Jennifer Blagg, one of the attorneys handling Van Dyke's appeal, said Monday the request to the Illinois Supreme Court "is an extraordinary remedy" that is only appropriate when there is an unquestionable fact or when an unquestionable law wasn't applied.
"That's not an appropriate remedy in Mr. Van Dyke's case because the law is clear, and the judge complied with the law when he sentenced Mr. Van Dyke to second-degree murder," she said, reading a statement to reporters.
"Let's be clear, the filing today is purely political. This case has always been about politics and it continues to be about political decisions," Blagg said.
"This case has come to represent all wrongs, perceived wrongs, of the Chicago Police Department," she said.
Martin Preib, second vice-president of the Fraternal Order of Police, Lodge 7, said the union is "disappointed with the political decision by Attorney General Kwame Raoul to challenge the sentencing of Jason Van Dyke."
"We believe Judge Gaughan sentenced Jason in the only manner the law allows," he said in the statement.
Van Dyke had argued he fired in self-defense after he said McDonald lunged at him with a knife. But a Chicago police dashcam video -- which a judge ordered the city to release 13 months after the shooting -- showed McDonald walking away from police, rather than charging at them.
The release of the video led to protests and a national conversation about police use of deadly force.
Van Dyke has been in custody since his conviction in October.