MADISON, Wis. -- A detective investigating the slaying of a University of Wisconsin-Madison student is urging a judge not to release audio of the 911 call she made before her death.

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Detective John Summers said Friday that the recording of the call from Brittany Zimmermann is a crucial piece of evidence and releasing it would hinder efforts to catch her killer.

Summers was among several witnesses who testified Friday in Dane County Circuit Court as Judge Richard Niess considered a lawsuit brought by media outlets seeking to force release of the call under the state's open records law.

Summers said the tape's release could prompt suspects to falsely confess if they know its content -- something he said already happened once in the case.

An investigator also testified that the tape's release could compromise the investigation.

"As a police officer conducting investigations and my years as a detective and the homicides that I've been associated with -- and the ones I've been a case detective or a co-case detective on -- is that information that I would want released? And I said, 'No,'" said Randall Bermeister, an investigator with the district attorney's office.

But Gregory Conway, an attorney for the media group that filed the lawsuit, argued that the public has a right to know what happened.

Conway questioned Mary Schauf, of the Madison Police Department, who has listened to the 911 call tape.

"Would you agree that the media in this case have a legitimate interest in following this story and presenting both sides of the issue to the public on whether or not certain functions of county government -- involving life and death -- are or have been properly conducted? Does the public have the right to know that?" Conway asked.

Schauf replied, "Yes."

But Suzanne Beaudoin, director of the Dane County District Attorney's victims witness unit, also testified Friday that the tape's release could be detrimental to the Zimmermann family, even destroying their ability to recover.

The Zimmermann family was in the courtroom Friday. Last week, Zimmermann's parents, Jean and Kevin Zimmermann, sent a letter to the Dane County judge asking the judge to reject the request to release the tape.

Niess said he plans to issue a ruling on Monday.

Zimmermann, a 21-year-old Marshfield native, apparently made the 911 call before she was killed in her campus-area apartment on April 2.

The 911 call has been the source of controversy for months. According to county officials, the call was mishandled by a 911 dispatcher. The attorney for the media outlets is arguing that with the 911 center's apparent mishandling of the call, the public deserves to know the exactly what happened and why, WISC-TV reported.

A warrant made public earlier this month said the call that lasted 57 seconds contains the sounds of screaming and a struggle.

Dane County 911 center officials said the operator couldn't hear those sounds, didn't call back the number as required and didn't send any officers to investigate. No officers were dispatched to the area where the cell phone call originated until 48 minutes later, after Zimmermann's fiancé found the woman dead.