Detective Dante Servin was off-duty when 22-year-old Rekia Boyd was shot last year after he got into an argument with a group of men who were nearby.
The charges Monday came seven months after the city settled a lawsuit with Boyd's family.
The city of Chicago did in fact settle with Boyd's family in an out-of-court settlement for $4.5 million earlier this year. The city acknowledged no fault.
The question ever since the March 2012 shooting was would criminal charges be brought against the off-duty officer involved and Monday the State's Attorney gave her answer.
Boyd was fatally shot in the back of the head as she walked with three others near Douglas Park. She was hit by one of five shots fired by Servin, who was in his car near his home, and had complained about too much noise in the wee hours of an unseasonably warm March night.
Servin claimed that a man with Boyd pulled what appeared to be a gun from his waistband, and Servin fired at him.
The state's attorney says the man, Antonio Cross had a cellphone, not a gun, and that Servin's action, shooting into a group of people, was reckless.
"Ms Erika Boyd lost her life for no reason and this defendant's actions were reckless in shooting in that alleyway that was occupied," said Cook County State's Attorney Anita Alvarez.
Servin, with 22 years on the police department, was charged Monday with involuntary manslaughter, reckless conduct and reckless discharge of a firearm. After he was informed of the charges, he came to the courthouse himself, where he was joined by a couple dozen of his colleagues.
"It's a sad day when a Chicago police officer is charged for something he was trained to do when defending himself," said Pat Camden.
One of Servin's five rounds hit Cross in the thumb. The other hit Boyd in the head as she was running away. Servin's colleagues insisted Monday that Cross did have a gun and that the detective acted appropriately.
The State's Attorney disputes that, and says that the actions of an off-duty cop warrant criminal charges.
"There's no evidence we can tell than any of them had a weapon in their hand," Alvarez said.
In his 22 years on the force, Servin has received numerous commendations. He was freed on bond after his court appearance Monday. He will be formally stripped of his police powers Tuesday.