A lawyer representing the Chicago police officer charged in Laquan McDonald’s shooting death is asking that the first-degree murder charge be dismissed.

Attorney Daniel Herbert filed a motion Tuesday. He contends that statements Jason Van Dyke and other officers gave investigators helped build the case against Van Dyke even after the officers were assured they wouldn’t be used “against them in any criminal proceedings.”

Van Dyke, who is White, shot the Black, 17-year-old McDonald 16 times in 2014.

The shooting of Laquan McDonald sparked outrage in the city of Chicago and was a catalyst for citywide protests. Members of the defense team are arguing that the teen’s juvenile record is important because his history of criminal activity and psychological issues; along with drug use—Laquan allegedly had PCP in his system at the time of the shooting—can help their murder defense.

The 2015 release of official police reports that directly contradicted video evidence of McDonald’s shooting by Van Dyke turned a spotlight on longstanding concerns about a “code of silence” in Chicago’s police force, in which officers stay quiet about or conceal possible misconduct by colleagues.

Judge Vincent Gaughan hasn’t made a ruling. The special prosecutor in the case, Joseph McMahon, says he’ll respond to the motion by the next court date, Feb. 3.

Gaughan ordered the release of McDonald’s juvenile records to Herbert, but hasn’t ruled whether the material can be used at trial.