The Federal Court's Justice Nye Perram is being asked to determine whether internet providers iiNet, Adam Internet, Dodo and others should have to identify customers that United States company Dallas Buyers Club LLC alleges infringed its copyright by sharing online the film of the same name.

If successful, Dallas Buyers Club LLC plans to send letters to those identified threatening to sue them or asking them to settle for thousands of dollars.

On Wednesday, Justice Perram heard closing submissions from defence lawyer for iiNet and the other internet providers, Richard Lancaster, on why Dallas Buyers Club LLC should not be provided with their customers' details.

The case featured testimony by Daniel Macek, a witness from the German firm Maverick Eye UG, which was employed to uncover the alleged pirates. He told the court last week that he was not able to interpret key log files.

It was also revealed under cross-examination that Mr Macek did not prepare his own expert witness affidavit and that it was instead prepared by the firm involved in the case that is trying to protect its copyright.

But on Wednesday, Justice Perram rejected iiNet's earlier attempts to make Mr Macek look inexperienced with the Maverick Eye software.

He also rejected iiNet's argument that it was improper for Mr Macek to not write his own affidavit.

"I would not conclude that there was anything improper going on," Justice Perram said of Mr Macek's affidavit, adding that the cross-examination of Mr Macek was at times "colourful".

"I thought the questioning of Mr Macek was quite unfair," Justice Perram said.

"You cross-examined Mr Macek [as though he was an expert]. He wasn't. He was just the guy in the room pressing the button," he told Lancaster.

"You tried to dress him up as an expert. He didn't know about the .pcap files [detailing alleged piracy]. Why would he?"

Justice Perram then detailed how it wasn't Mr Macek who should have been asked about the so-called .pcap files showing alleged piracy conducted by 4726 IP addresses of internet account holders in Australia.

The files are central to the case and were made using the Maverick Eye piracy-hunting system, which connects to alleged infringers' computers to download small files which Dallas Buyers Club and Maverick Eye UG say confirm they are committing online copyright infringement.

Justice Perram instead said Dr Simone Richter, a German-based IT professional who provided expert witness testimony to the case based on Mr Macek's company's piracy-hunting software should have been asked about the files.

But Lancaster argued that it was not apparent from Mr Macek's affidavit that he was an inexperienced 30-year-old who didn't know the details of the operation of the Maverick software.

Lancaster told the judge Mr Macek's affidavit read like an expert report and that he "didn't know how young" he was and presumed he would be able to answer the questions.

In response, Justice Perram said he was making no criticism of Lancaster and appeared to agree that the defence team couldn't have foreseen that, as things turned out, Mr Macek was not the person to deal with the questions, saying "you didn't really know who Mr Macek was going to be".

But the judge added that had Dr Richter been questioned, it would've been "very likely" had Lancaster asked about the .pcap question that he "may well have got answers from a witness that knew about it.

"And yet she wasn't [called upon from cross-examination]," the judge said.

The .pcap files are what detail the timestamps of when infringing files were allegedly shared on the internet using peer-to-peer file-sharing technology.

Lancaster had previously argued that the timestamps in the .pcap files were not a true indication of the times the files were shared and were therefore not reliable evidence, as IP addresses can change.

But Justice Perram said that it would have to be a "coincidence of galactic proportions" for all the IP addresses to be inaccurate and that it shouldn't be an excuse to dismiss the case.