JOLIET, Ill. (CBS) — A special prosecutor will oversee the driving under the influence case against off-duty Joliet police Officer Erin Zilka, who was charged in a crash that killed an off-duty Berwyn police officer on Sunday.

The Will County State’s Attorney James Glasgow requested a special prosecutor in the case. Glasgow said Zilka is the victim in an aggravated battery case tied to her job as a police officer, and also is a witness in another case his office is prosecuting.

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“The prosecution of the defendant by the State’s Attorney’s Office could create the the appearance of an impropriety. It is in the interest of justice that a Special Prosecutor be appointed to avoid any such appearance,” Glasgow wrote.

Erin Zilka, a Joliet police officer, is charged with DUI in a crash that killed Berwyn Police Officer Charles Schauer. (Credit: Illinois State Police)

Will County Chief Judge Richard Schoenstedt agreed to Glasgow’s request, and will first request that either the Illinois Office of the State’s Attorney Appellate Prosecutor or the Illinois Attorney General’s office serve as special prosecutor in the case. If those offices do not agree to handle the case, the judge could then request that other county state’s attorneys from Illinois take the case.

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Zilka is charged with driving under the influence and and driving too fast for conditions.

Illinois State Police have said Zilka was driving and Berwyn police Officer Charles Schauer was in the passenger seat of a Dodge Durango, when she crashed into a box truck that was blocking traffic on Interstate 55 near Plainfield, following an earlier crash involving a pickup truck.  Schauer was pronounced dead at the scene.

Officer Charles Schauer

Berwyn police Officer Charles Schauer was killed in a traffic crash. (Credit: Berwyn Police)

Zilka’s attorney said her blood alcohol level was under the legal limit, though experts have said there are other factors that can go into a DUI charge.

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She is due back in court in March.