Magnotta, who is facing a first-degree murder charge in the slaying of Chinese student Jun Lin last year, granted the interview as part of a 2007 study on sex-trade workers and their clients.
Authorities want a copy of the interview for evidence they're still gathering against Magnotta.
A lawyer for the University of Ottawa academics who conducted the interview argues the material is covered by privilege as Magnotta was guaranteed confidentiality when he agreed to participate.
Superior Court Justice Sophie Bourque said today she'll rule on the matter at a later date.
She says she is not ruling out looking at the contents of the interview and that she must balance the issue of privilege versus public interest.
Police became aware of the existence of the interview when a research assistant contacted them after seeing a news item about Magnotta's arrest last year.
The Crown says it doesn't know what's in the interview, but wants the judge to have a look before deciding to quash a Montreal police warrant and giving the material back to the researchers.
The lawyer for the academics argued it's unlikely the material would have much impact on a case involving charges for crimes allegedly committed five years after the interview.
He also urged Bourque to look at the material only if it is absolutely necessary.
A lawyer for Magnotta's defence team supported the motion filed by the researchers to keep the interview confidential, but made it clear they will ask for a copy of it for themselves.
Magnotta's preliminary hearing, which is to determine whether he'll have to stand trial on the murder charge, resumes Monday.
Evidence presented at the hearing is subject to a publication ban.
Magnotta has pleaded not guilty to five charges and opted for a jury trial.