Heaven Sutton was struck in the back by a stray bullet from gang crossfire in 2012 on the West Side.
WATCH: Trial begins for man accused of killing 7-year-old girl
"She wanted to be a singer, a police officer and a dancer," said Ashake Banks, Heaven's mother.
Dorsey's trial began on Monday. Several witnesses took the stand at the Cook County criminal courthouse, including the little girl's brother, who was there when she was shot and positively identified Dorsey as her killer out of a police lineup.
Two brothers, including one who was injured in the exchange of gunfire that night, also testified. Prosecutors were frustrated that they refused to acknowledge signed statements they gave police in the immediate aftermath of the incident which also identified Dorsey, known by the nickname JJ, as the shooter.
On Monday, Banks, who is now an outspoken critic of gun violence in Chicago, dressed nearly head to toe in pink, her daughter's favorite color. After the guilty verdict was read, she said she finally has gotten justice.
"To shoot in the crowd and kill a 7-year-old, and he walked in the courtroom like he killed a 30-year-old gang member. You just don't do that. He didn't have no remorse, his family didn't have no remorse," Banks said. "They come in the courtroom and look at me and roll their eyes. I didn't kill Heaven, your son did."
Dorsey's family and friends walked out of the courtroom spewing profanity, as Banks headed to the cemetery to visit her daughter, who she calls her butterfly.
Dorsey remains locked up in Cook County Jail, where he has been for the last several years. He faces life in prison.