CHICAGO (AP) — A Chicago man currently serving a 90-year prison sentence for beating and raping a prostitute has been found guilty of sexually assaulting and murdering another woman.

The Chicago Sun-Times reports (http://bit.ly/1Tr2YZ2 ) Michael Johnson was convicted Friday in the January 2010 death of Leslie Brown. The body of the 28-year-old Brown was found in an abandoned building.

In closing arguments before Cook County Circuit Judge Joseph Kazmierski, Assistant State's Attorney Alex del Castillo said the 29-year-old Johnson thought he committed the "perfect crime" by killing a prostitute. He said the defendant believed Brown had slept with so many men detectives would never trace evidence back to him. Castillo noted it was only Johnson's DNA found inside Brown's body.

Brown now awaits trial for allegedly murdering at least two other women and leaving another for dead.