Nearly 2 1/2 years after Chicago police and Cook County prosecutors began videotaping murder confessions, the unraveling of a murder case with a taped confession underscores why some lawmakers and advocates have called for further reform, including recording entire interrogations.

Although police in Chicago and elsewhere have vigorously opposed taping interrogations, some legal experts said the case--in which a man who had been held for 50 hours falsely confessed to killing his mother--exposes the limits of taping only the confession.

"If you don't see the interrogation, you're missing almost everything," said Welsh White, law professor at the University of Pittsburgh. "You don't see the questions the police ask, the tactics they use, the pressures they might exert."

Even before Friday's release of Corethian Bell--the first time in Cook County that a videotaped confession has come undone--there had been limited efforts to expand taping.

Illinois House Speaker Michael Madigan (D-Chicago), the legislature's leading advocate of videotaping, is expected to renew his push for a law that would require authorities to videotape interrogations in major violent crimes.

And Cook County State's Atty. Richard Devine, whose office led the prosecution of Bell for the 17 months he was in jail, has said that he would support a pilot program to test the videotaping of interrogations.

The problems in the Bell case were detailed in the Tribune investigation, "Cops and Confessions," which showed how dubious confessions had marred hundreds of Cook County cases. The series found that police tactics ranging from coercion and brutality to illegal arrests had produced confessions so tainted that they were thrown out or defendants were acquitted.

Because the interrogation process takes place behind closed doors, legal battles over the validity of confessions often boil down to the word of police versus the word of the suspect.

But videotaping, some advocates say, could help clarify those issues because the tape could answer what really went on during the interrogation. In that way, taping might help police and prosecutors as much as it aids defendants--and police departments that regularly tape interrogations report that the change was for the better.

"If you're really in a quest for justice, you ought to be continually looking for superior ways of determining the truth," said William Geller, a national expert on police practices and the author of a U.S. Justice Department report on videotaping interrogations. "And taping the interrogation is superior."

Critics, though, say videotaping interrogations would be costly and that it would impede investigators as they try to get legitimate statements.

Chicago police and Cook County prosecutors began videotaping murder confessions--but not interrogations--in August 1999, nearly a year after they were forced to drop charges against two young boys accused of the murder of 11-year-old Ryan Harris. Since then, they have taken more than 400 video confessions in murder cases.

Bell, 25, was charged with the July 2000 murder of his mother, Netta, after he made a videotaped confession in which he said he stabbed her to death because she had resumed her cocaine habit.

Bell, who is mildly mentally retarded and has a long history of mental illness, said in court documents that he confessed because police hit him so hard that he was knocked off a chair and because he grew weary and hopeless after being in custody for more than two days.

He said he believed that once in front of a judge he could explain that he was innocent and the judge would set him free. Instead, he was prosecuted and jailed.

Cook County prosecutors dropped charges Friday after a final round of DNA testing failed to link him to the crime. Instead, the tests have connected another man already in jail for a crime similar to Netta Bell's murder. That man, prosecutors said, remains under investigation, although he has not been charged in Netta Bell's murder.

One of Bell's lawyers, Herschella Conyers, said videotaping the interrogations that produce confessions is a crucial step in preventing false admissions.

"You can't not tape the 50 hours of denials, and not tape the time the police strike someone in the head, and not tape the way the person is coached into saying whatever he says, and then only flip on the camera for the actual confession," said Conyers of the University of Chicago's Mandel Legal Aid Clinic.

"You have to tape everything that leads up to it."