After Robert Head was slain in a knife fight over drugs on the south side of Chicago on April 3, 2002, police found a bloody knife nearby. Police sent the knife to the Illinois State Police crime laboratory, which in turn sent it to a private forensic laboratory, Orchid Cellmark, for DNA analysis. On April 26, three weeks and two days after the crime, Maurice Patterson, 35, was arrested and identified by several witnesses. Based solely on those lineup identifications, Patterson was charged with the murder.
On September 18, 2002, Orchid Cellmark notified the State Police Forensic Science Center that the blood on the knife was a mixture of the victim's blood and the blood of an unknown person. The State Police then ran the unknown person's DNA profile through the state Combined DNA Index System (CODIS) and identified him as James Starkey, a drug addict with a record of violence. On February 3, 2003, the State Police sent a report to Dolores Myles, a Chicago police detective assigned to the case, saying that Starkey's blood was on the knife. A copy of the report was sent to Kathleen Van Kampen, an assistant Cook County state's attorney prosecuting the case. The report did not mention that Head's blood had been found on the knife, although it referenced Cellmark's September 18 report, which had said that.
The prosecution of Patterson proceeded before Cook County Circuit Court Judge James B. Linn. At a pretrial hearing on February 26, 2003, Linn asked Van Kampen about the forensic analysis of the knife. She responded that her "best guess" was that the knife was not the murder weapon because the DNA on it came neither from Patterson — true — nor from Head — false. At Patterson's three-day jury trial in November 2003, Detective Myles testified that Head's DNA was not on the knife. Patterson's lawyer, Assistant Public Defender Robert Strunk, did not challenge that incorrect assertion. In closing argument, Assistant State's Attorney David Weiner, Van Kampen's trial partner, told the jury the knife could not have been the murder weapon because Head's DNA was not on it. Based on in-court identifications of three eyewitnesses, the jury found Patterson guilty.
At his sentencing in February 2004, Patterson professed innocence — "I didn't kill that man. I never saw that man, never in my life" — vowing that he would be back and asking Linn, "[A]re you going to apologize to me?" Linn sentenced him to 30 years in prison. In November 2007, Patterson filed a Freedom of Information Act request and obtained copies of the forensic reports in the case with the names blacked out. In October 2009, the Cook County State's Attorney's Office informed Patterson's appellate lawyer that — contrary to the claims at trial by Detective Myles and Assistant State's Attorneys Van Kampen and Weiner — Head's DNA was on the knife along with Starkey's DNA. By agreement, the case was remanded to the trial court for further proceedings.
Karen Daniel, a staff attorney at the Center on Wrongful Convictions, entered the case as Patterson's attorney. The State joined in a motion to vacate Patterson's conviction, which Judge Linn granted on November 23, 2009. The prosecution, however, did not dismiss the charges until nearly a year later, on October 8, 2010 — after Patterson's legal team discovered a multitude of additional evidence of Patterson's innocence and moved for dismissal of charges based on due process violations. Patterson was granted a certificate of innocence by the Circuit Court of Cook County on May 5, 2011.