(CNN) The Illinois Supreme Court denied a request Tuesday by the state's attorney general to resentence former Chicago police Officer Jason Van Dyke in the murder of black teenager Laquan McDonald.

Attorney General Kwame Raoul and Joseph McMahon, the special prosecutor who tried the case, were seeking to increase the length of Van Dyke's sentence. In February, they filed a petition challenging the legality of his 81-month prison sentence handed down in January by Cook County Circuit Court Judge Vincent Gaughan.

Van Dyke's attorney, Dan Herbert, said he and his client were pleased with the court's decision.

"Our judicial system may not be perfect. However the bedrock of the system maintains that all defendants, including unpopular ones, are entitled to fair and impartial treatment," Herbert said in a statement. "Jason Van Dyke is prepared to serve his debt to society and move on with his life in a meaningful and productive manner."

Van Dyke, who is white, was convicted in the death of McDonald, 17, but was sentenced only "based on his conviction for second-degree murder and not the more serious charges of 16 counts of aggravated battery with a firearm," a statement from the attorney general's office said.

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