Image caption The US Copyright Group promises to help copyright owners recoup losses

US civil liberties group the Electronic Frontier Foundation will give evidence in a Washington court on Wednesday, aimed at stopping the US's largest net pirate hunt.

It wants the court to throw out thousands of lawsuits against alleged illegal file-sharers, brought by the US Copyright Group.

EFF argues the mass litigations deprive individuals of a fair trial.

The case has implications for other countries pursuing similar cases.

The US Copyright Group, a Washington-based law firm, has filed lawsuits on behalf of seven film-makers, accusing over 14,000 individuals of downloading films illegally, including Oscar-winning movie The Hurt Locker.

High stakes

EFF will argue that mass litigation is unfair.

"We contend that these suits improperly lump thousands of defendants together, a shortcut that deprives the defendants of fair access to individual justice," EFF said in a statement.

A federal court in Washington DC will hear oral arguments from the EFF on Wednesday.

USCG has been sending letters to identified illegal file-sharers asking them to pay a fine of around $1,500 - $2,500 (£1,000 - £1,670) or face a copyright suit of up to $150,000 (£100,000).

"The stakes are high for anyone identified in USCG's slipshod cases. USCG's strategy appears to be to threaten a judgement of up to $150,000 per downloaded movie - the maximum penalty allowable by law in copyright suits and a very unlikely judgement in cases arising from a single, non-commercial infringment," EFF said in a statement.

The threat "puts pressure on alleged infringers to settle quickly", it added.

EFF and other groups have been concerned about the tactics being employed by some law firms pursuing alleged file-sharers.

The methods used to track down infringers are not fool-proof because they identify the computer that downloaded the material rather than the actual individual.

In some cases, alleged file-sharers could be the victim of wi-fi hijacks, where someone uses an unsecured network to steal music and films.

Form fillers

In the UK, consumer watchdog Which? has been highlighting cases where people have been wrongly accused of file-sharing.

The allegations have come from law firm ACS: Law which has sent thousands of letters identifing illegal file-sharers and offering them the option of a one-off £500 fine or court action.

Which? reports this week that the firm is now sending questionnaires to alleged file-sharers who deny they were responsible for illegal downloading.

The questionnaire asks users to submit their computers to a forensic examination and answer other questions about their computer connection.

"We believe this is the latest example of bullying behaviour by ACS Law, which says that if people don't complete its questionnaire, it has no option but to consider them guilty. Declining to fill in a form is not evidence of guilt," said Deborah Prince, Which's head of legal affairs.

ACS: Law has said its actions are legitimate, given how big a problem illegal file-sharing is for the music and film industries.

"It is the equivalent of someone stood outside HMV with a pile of the latest albums, handing them out to people who were intending to go in the shop and buy it," ACS: Law partner Andrew Crossley told the BBC.

To date the US Copyright Group has declined to comment despite requests from the BBC.