Sharman Networks turned up the heat on three record label representatives in the Federal court on Thursday, attacking the labels' spoof files campaign.
Senior counsel for Altnet, Steven Finch, examined the three on their claims that the spoof files accounted for only a small part of the Kazaa network.
Sharman's lawyers have previously questioned the record labels' claims about the proportion of unauthorised, authorised and spoof files shared on Kazaa.
The record labels employed US company MediaDefender to help flood Kazaa with spoof files, the court heard.
Spoof files appear to Kazaa users as quality sound recordings, but once downloaded result in garbled recordings.
Finch first challenged Des Dubery, director of legal and business affairs at BMG Australia, to explain the basis of his claim that spoof files were a small part of Kazaa.
Dubery said he had consulted a BMG colleague who had tested some spoof files, and had read about the files in the media.
Finch claimed Dubery had based his claims on the views of others, and had not verified the number of spoof files.
BMG paid MediaDefender to provide reports on what files were used by Kazaa, but "you [Mr Dubery] don't know what these reports from MediaDefender say," Finch said.
Finch asked similar questions of Damian Rinaldi, director of business affairs at Sony Music Australia, and Karen Don, director of legal affairs at Universal Music Australia.
Like Dubery, Rinaldi said he had not seen MediaDefender reports on the scope of the spoofing campaign, but based his claims on advice from a colleague.
Later in the day's proceedings, the record labels called Tom Mizzone, of US anti-piracy firm MediaSentry, to the witness box.
Questioned by Tony Bannon, SC, the labels continued to press their point that copyright infringers on Kazaa could be identified by ordinary means.
Earlier in the day, Justice Wilcox ruled that 12 Sharman affidavits that argued the benefits of open content licenses would not be considered in the trial.
The affidavits of support ranged from record labels to Internet archive projects, such as Project Gutenberg.
However, Justice Wilcox said authorisation of copyright infringement, not the potential non-infringing use of peer-to-peer technology, was the central issue in the case.