In the first US trial to challenge fines levied by music companies for sharing copyrighted music online, a single mother from Minnesota has gone to court to prove she did nothing wrong.

Jammie Thomas is the first among more than 26,000 people sued by the world's most powerful recording companies to refuse a settlement after being slapped with a lawsuit by the Recording Industry of America and seven major music labels.

Unlike some who insist on the right to share files over the Internet, Thomas says she was wrongfully targeted by SafeNet, a contractor employed by the recording industry to patrol the Internet for copyrighted material.

"I did not download or upload any music, period," Thomas, 30, said outside the federal courthouse in Duluth, where a 12-member jury was empanelled Tuesday.

Instead of paying a few thousand dollars to settle the suit, Thomas will spend upwards of 60,000 dollars in attorney's fees because she refuses to be bullied, her lawyer said.

"No one can prove which computer actually did this," defense attorney Brian Toder said in his opening statement.

He argued that someone else could have easily hijacked her Internet address in order to upload songs on the Kazaa file sharing network.

But industry lawyers said there is clear evidence that Thomas, an employee of the Mille Lacs Band of Ojibwe, a native American Indian tribe, shared more than 1,700 songs with potentially millions of computer users.

"Piracy is a tremendous problem affecting the music industry," said the first witness, Jennifer Pariser, head of litigation and anti-piracy for Sony BMG Music Entertainment, the second-largest record company in the world.

Rather than pursue Thomas for all 1,072 songs in the public folder found on Kazaa, she is being sued for sharing just 25 songs by Virgin Records, Capitol Records, Sony BMG Music Entertainment, Arista Records, Interscope Records, Warner Brothers Records and UMG Recordings Inc.

But her liability for allegedly sharing Godsmack's "Spiral," Destiny's Child's "Bills, Bills, Bills," Sara McLachlan's "Building a Mystery" and others could be as high as 150,000 dollars a song if the jury finds "willful" copyright infringement.