CHICAGO — The Cook County, Ill., state's attorney's office on Tuesday contended student investigators from Northwestern University's Innocence Project paid a witness in its investigation to exonerate a man convicted of murder in 1982.

"This evidence shows that Tony Drakes gave his video statement upon the understanding that he would receive cash if he gave the answers that inculpated himself and that Drakes promptly used the money to purchase crack cocaine," according to a filing made by prosecutors Tuesday. The filing argues the students acted as investigators, not reporters, and as such aren't protected by press rights.

Prosecutors allege that after conducting a 2004 interview with Drakes, a private investigator working with students paid a cab driver $60 to take Drakes from the interview site, a park in downstate Swansea, to a gas station two miles away. That amount was more than the fare and tip, and leftover cash — $40 — was given to Drakes; he used it to buy crack at a nearby crackhouse, the filing states.

David Protess, a professor in the university's Medill School of Journalism and the director of the Innocence Project, refuted any claim that a student paid Drakes for the statement, in which Drakes implicates himself in the killing.

Judge Diane Cannon accepted the prosecutors' filing and scheduled the next hearing in the case for Jan. 11.

The Innocence Project in 2003 took on Anthony McKinney's case and helped him win a new day in court.

But as they prepare for the hearing on McKinney's fate, prosecutors seem to have focused on the students and teacher who led the investigation. Last month the state's attorney subpoenaed the students' grades, notes and recordings of witness interviews, the class syllabus and even e-mails they sent to each other and to Protess.

Northwestern has turned over documents related to on-the-record interviews with witnesses that students conducted, as well as copies of audio and videotapes.

But the school is fighting the effort to get grades and grading criteria, evaluations of student performance, expenses incurred during the inquiry, the syllabus, e-mails, unpublished student memos, and interviews not conducted on the record, or where witnesses weren't willing to be recorded.

"I don't think it's any of the state's business to know the state of mind of my students," Protess said last month. "Prosecutors should be more concerned with the wrongful conviction of Anthony McKinney than with my students' grades."

According to Tuesday's filing, Drakes told the state's attorney's office that the students knew he was looking for money, and he knew they wanted help with McKinney's case. McKinney has been in prison for 31 years.

Drakes told prosecutors that he had a 7 p.m. curfew the night of the interview, and that the Northwestern students initially said they wouldn't pay for his statement, but that one student later "flashed a wad of cash" at him, according to the filing.

After the student paid the cabbie, the driver recorded the transaction in his log, Tuesday's filing states. Apparently suspicious that it was a drug deal or a sting, he wrote: "detective gave me 60, told me to give him 40, gave me 60 ... gave him change." The "him" refers to Drakes.

According to the filing, the driver's log notes the fare for the two-mile trip to the gas station—normally about $6 — was $20. "The driver did not claim his $14 tip, he was worried it was drug money," the filing states.