After spending three years investigating the conviction of a Harvey man accused of killing a security guard with a shotgun blast in 1978, journalism students at Northwestern University say they have uncovered new evidence that proves his innocence.

Their efforts helped win a new day in court for Anthony McKinney, who has spent 31 years in prison for the slaying. But as they prepare for that crucial hearing, prosecutors seem to have focused on the students and teacher who led the investigation for the school's internationally acclaimed Medill Innocence Project.

The Cook County 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 professor David Protess of the university's Medill School of Journalism.

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

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and grading criteria, evaluations of student performance, expenses incurred during the inquiry, the syllabus, e-mails, unpublished student memos, and interviews not conducted on the record, or where witnesses weren't willing to be recorded.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. "Prosecutors should be more concerned with the wrongful conviction of Anthony McKinney than with my students' grades."

Prosecutors declined to discuss the request for grade reports, but a spokeswoman said the subpoena is about seeking truth in the case.

"They have material that's relevant to the ongoing investigation, and we should be entitled to that information," said spokeswoman Sally Daly.

Don Craven, acting executive director of the Illinois Press Association, said the request seems harassing at best, and at worst looks like an attempt to discredit the work done by the Innocence Project to ferret out wrongful convictions.

"They're either trying to undermine the investigation, or they're trying to undermine the entire project," Craven said.

Turning over such a wide range of information, he said, would cripple the Innocence Project's ability to get witnesses to cooperate in the future.

Richard O'Brien, the lawyer representing the university, said it's an unwarranted fishing expedition that focuses on the messenger -- rather than on the possibility that an innocent man has spent more than three decades behind bars. Prosecutors, he said, "seem to be peeved" at the Innocence Project for uncovering a wrongful conviction.

Former student Sarah Forte said a prosecutor implied to her that students might have been pressured to find evidence that McKinney was innocent or else they would get poor grades in the class.

"I think it's frustrating and sad," said Forte, who graduated from Northwestern in 2006 and now works for the Southern Center for Human Rights, which conducts similar investigations.

Since the Innocence Project began in 1999, Protess and his students have uncovered evidence that helped free 11 innocent men, according to a class Web site.

The cases included the Ford Heights Four, exonerated of the 1978 murders of a suburban couple. Another case centered on Anthony Porter, who came within 50 hours of execution in 1998 before he won a reprieve. Examination of the Porter case by an investigative reporting class taught by Protess helped trigger the Innocence Project's creation.

Those investigations and others spurred headlines and policy changes. Former Illinois Gov. George Ryan, now serving time in federal prison on corruption charges, had credited the project's investigations with helping him decide to halt executions in January 2000. Before leaving office in 2003, he granted clemency to all death row inmates.

The project's most recent effort focuses on McKinney and on a crime that happened Sept. 15, 1978.

Donald Lundahl, a security guard in south suburban Harvey, was sitting in his car about 9:30 p.m. when someone shot him.

Later that evening, police saw McKinney, 18, running down the street near the crime scene. He told them he was fleeing gang members. Initially held for questioning and released, McKinney remained a prime suspect.

Another Harvey teenager told police he saw McKinney kill Lundahl. After a lengthy interrogation, McKinney signed a confession and was charged with first-degree murder.

The Innocence Project began to examine the case in October 2003 at the request of McKinney's younger brother. The effort continued over three academic years, until June 2006.

In November 2008, Protess laid out on the project's Web site what his students reportedly uncovered.

They tracked down the witness who originally fingered McKinney for police. He recanted his story in a videotaped interview, saying police beat him until he made up the details about McKinney's involvement, according to the Web site.

The students also interviewed two admitted gang members said to have chased McKinney on the night of the murder; they corroborated his story.

"Angry that Anthony had recently damaged their car, they admitted pursuing him after a chance encounter," Protess wrote on the Project's Web site.

Seven others who were identified as witnesses told the students about a man who they said admitted years ago to the killing. The students tracked him down.

In a videotaped interview, the man said he was present during the murder and that McKinney was not there. The reputed witness identified two people he claimed were the real killers, according to the Innocence Project investigation.

Protess said his students talked to one, now living in Racine, Wis., who denied involvement. The other, jailed on an unrelated crime, declined to talk to them.

In 2006, the students took their findings to the Center on Wrongful Convictions at the Northwestern law school's Bluhm Legal Clinic. A year ago, it filed a petition on McKinney's behalf for a hearing in Cook County Circuit Court.

The state's attorney did not seek to have the petition dismissed and agreed that a hearing should be held. So far, a date has not been set. A judge will decide whether the evidence warrants a new trial for McKinney.

Prosecutors argue in court documents that they need the school information to make "an accurate assessment of witnesses' credibility and other essential issues," also saying that their own investigation uncovered credibility problems with the people interviewed by the students.

Because government investigations are regulated by strict ethical and disclosure guidelines, a full explanation of the school's procedures is necessary to ensure justice, prosecutors said in court papers.

"Without full disclosure, the potential for great abuse will increase as private entities conduct their own investigations," the court documents said.

Prosecutors also have asserted that the Medill students and their professor are not journalists and, therefore, not protected from revealing sources and turning over notes under the Illinois Reporter's Privilege Act.

It's a contention that John Lavine, dean of the journalism school, called false -- and irrelevant.

Said Lavine, "They took reporting to the nth degree."