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Three current and former Chicago police officers charged in the Laquan McDonald case pleaded not guilty in their first court appearance on Monday as the judge presiding over the case recused herself, NBC Chicago reported.

Former detective David March and officer Joseph Walsh, as well as current officer Thomas Gaffney, were indicted last month on charges of conspiracy, official misconduct and obstruction of justice for allegedly attempting to interfere with the investigation into the 2014 killing of the 17-year-old.

Judge Margaret Brosnahan recused herself moments before Monday's arraignment, giving no reason behind the decision, according to NBC Chicago. The officers later pleaded not guilty to the charges and were released on a $50,000 bond.

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All three officers were at the scene when Officer Jason Van Dyke fired the 16 shots that killed McDonald on October 20, 2014, according to special prosecutor Patricia Brown Holmes.

Gaffney, Walsh ─ Van Dyke's partner at the time ─ and lead detective March gave conflicting accounts of what occurred, allegedly in order to protect Van Dyke. They allegedly claimed that McDonald was swinging a knife at the time of the shooting.

Their reports were contradicted by dash cam footage released more than a year later, which showed the teenager moving away from the officers when he was shot. The video resulted in Van Dyke being charged with murder. He has pleaded not guilty.

Related: Officer Jason Van Dyke, Who Shot Laquan McDonald, Takes Stand at Hearing

"The indictment makes clear that these defendants did more than merely obey an unofficial 'code of silence,' rather it alleges that they lied about what occurred to prevent independent criminal investigators from learning the truth," Holmes said in a release in June.

March and Walsh have resigned from the force. Gaffney was suspended without pay after the indictment, a department spokesman said.

The three felonies carry sentences of up to five years in prison.

The officers are scheduled to appear in court again August 29.