The suit claims the acoustic introduction to 1971's "Stairway" was lifted from Spirit's 1968 instrumental "Taurus." The Wrap reports attorneys for plaintiff Michael Skidmore - trustee for the Randy Craig Wolfe Trust which, according to the papers, owns Wolfe's copyrights - slammed Led Zeppelin for questioning the validity of the trust in papers filed on Tuesday.

"There is no evidence to cast even the slightest bit of shade on the validity of the Trust, nor have Defendants argued that there is any real reason to doubt the validity of the Trust," the papers read. "This is a pure fishing expedition."