On May 3, 1986, two University of Chicago students were walking to their dormitories when they were approached from behind by three males. The men pushed the two women to their knees, demanding money and claiming to have a gun. Only one of the victims had money, six dollars, which she handed over. The assailants then told the victims to stand up and walk straight ahead. After a time, they came to an empty garbage lot, where one woman was sexually assaulted three times by one man and once by another. She scratched one of the assailants on the face and neck. The other woman was held by the third man and escaped being raped after a violent struggle. Wardell was picked up on a separate charge before he was identified as a perpetrator. A co-defendant and boyhood friend of Wardell, Donald Reynolds, was directly identified by both victims in a show-up, and a third suspect was never arrested.

A month after the incident, the rape victim tentatively identified Wardell from a photo line-up, though she said she was not certain because her attacker had been wearing a hood. In a second line-up with all the men in hoods and speaking a phrase uttered at the scene, the victim positively identified Wardell.

Wardell and Reynolds were charged with criminal sexual assault and armed robbery. The state's evidence against the men consisted of the victim's identification of Wardell and incorrect serological testimony connecting Reynolds to the crime. Pamela Fish, a forensic analyst, testified that blood group testing on semen from the crime could not exclude Reynolds and that 43% of the population shared his blood type. The victim also had blood group markers consistent with the crime scene sample, and the analyst failed to explain that her blood type could have "masked" the perpetrator's. When the evidence being tested is a mixed stain of semen from the perpetrator and vaginal secretions from the victim – and testing does not detect blood group substances or enzymes foreign to the victim – no potential semen donor can be excluded.

The two men were convicted and sentenced to 55 years in prison.

Fish's notes from the tests were found years later, saying that the blood types that she testified were consistent did not in fact match up. Another issue was that potentially exculpatory evidence, a June 1986 report on hair and fiber evidence, was never turned over to the defense. DNA testing was repeatedly requested (since the original trial) and finally granted in 1997.

Testing on the biological evidence revealed DNA profiles from two male sources, neither of whom could have been Wardell. Reynolds was also excluded, thus casting additional doubt on Wardell's conviction as his accomplice.

In November of 1997, Wardell's conviction was finally vacated. A new trial was granted but charges were dropped, setting Wardell and Reynolds free. They had each been incarcerated for eleven years.