Factual background: On March 18, 1983, a 9-year-old girl was walking to school when a man dressed like a police officer approached her. He then chased the girl, forced her into a car, drove to a nearby alley, and raped her. On April 18, 1983, in the same area, a 12-year-old girl reported that a man displaying a badge chased her, forced her into a car, drove to an alley, and raped her.

Bullock was charged in both incidents, but charges stemming from the second were dropped. Ronnie Bullock was convicted of aggravated criminal sexual assault by a Cook County jury in May 1984. A judge sentenced Bullock to 60 years in prison for deviate sexual assault and 15 concurrent years for aggravated kidnapping.

Prosecutor's evidence at trial: The prosecution based its case on several points:

· A police officer identified Bullock from a composite sketch compiled by the two victims.

· Both victims identified Bullock in a police lineup.

· Bullock lived in the area where the rapes occurred.

Postconviction challenges: Immediately following Bullock's conviction, he insisted that the evidence be impounded. This motion was approved, and the judge ordered that the victim's panties be stored in the circuit court clerk's office freezer. An appeals court upheld Bullock's conviction in March 1987. Bullock also filed a motion for postconviction relief, which was denied in October 1990. He then submitted a motion in 1993 to have the evidence released for DNA tests. The prosecution agreed to this motion; it was granted in June 1993. There was a delay, however, between the granting of the motion and Cellmark Diagnostics' test because some of the evidence (including the victim's panties) had disappeared. Bullock's attorneys eventually found the materials and sent them to Cellmark Diagnostics.

DNA results: The report from Cellmark Diagnostics, completed in October 1994, stated that PCR testing was performed on a sperm and nonsperm fraction of the victim's panties, a rectal swab, the blood of the victim, and the blood of Bullock. No conclusions could be reached from the rectal swab due to an insufficient quantity of human DNA. The report stated that Bullock was excluded as the source of both the sperm and the nonsperm fractions in the semen stain on the victim's panties.