Fairfax lawyers have asked the court to overturn a ruling forcing investigative journalists Richard Baker and Nick McKenzie into the witness stand in the committal of eight former banknote executives charged with bribery.

Editor-in-chief of The Age Andrew Holden has said the sources will not be revealed under any circumstances.

Defence barrister Campbell Thomson told the Supreme Court on Thursday that the sources of an article published the weekend before defence submissions were due to begin, on December 8, could have had ''mischievous'' intentions.

The article revealed that an Indonesian bagman would become a prosecution witness.

Mr Thomson suggested the sources could have supplied this information to have proceedings adjourned. If so, it would be ''the most appalling abuse of process''.

He said if the sources were police officers, members of the prosecution or government officials it could mean the charges should be dismissed.

Fairfax barrister Kristine Hanscombe, SC, said this was a ''conspiracy theory'' and there was ''no legitimate forensic purpose'' to identifying the sources.

She asked the court to review the ruling by magistrate Phillip Goldberg that supported the subpoenas, saying he had failed to consider crucial evidence that there was no ''misbehaviour'' by police. ''No AFP officer is the source,'' she said.

Justice Michael Sifris said he would deliver a decision before January 28.

Committal proceedings are to resume on February 4.