Led Zeppelin guitarist Jimmy Page took the stand on day one of the band's "Stairway to Heaven" trial, while the opposing lawyer was warned that his actions may be grounds for a mistrial.

Page and singer Robert Plant are in Los Angeles to battle claims they plagiarized the opening of Spirit's 1968 instrumental song "Taurus" on their landmark 1971 track "Stairway to Heaven." According to the Los Angeles Times, "Stairway" has generated $562 million dollars in publishing royalties and record sales since being released.

Due to the statute of limitations, Spirit songwriter Randy (California) Wolfe's estate is only able to seek revenue generated by the song from 2011 on. But as you can imagine, going forward that would still represent quite a hefty sum.

However, according to the Hollywood Reporter, Spirit's case may be in trouble already. Judge R. Gary Klausner has declared that a video played for the jury today by Wolfe estate attorney Francis Malofiy could be "grounds for a mistrial." The video in question reportedly shows a session musician performing the opening of "Stairway to Heaven," the bass line for "Taurus" and then both pieces synced together.

That's potentially a problem, if as Led Zeppelin attorney Peter Anderson objected, the video wasn't included in the joint list of exhibits submitted prior to trial. As of this report Anderson has yet to formally request a mistrial.

Meanwhile, as documented on Twitter by reporter Pamela Chelin, Page took the stand to contradict claims that he witnessed Spirit performing when the two bands shared a 1968 bill in Denver, Colorado. He also revealed that while he remembers obtaining Spirit's second and third albums (The Family that Plays Together and Clear, both from 1969), he doesn't recall purchasing or hearing their self-titled 1968 debut, which contains "Taurus."

However, he went on to admit that the album in question has since made its way into his collection of 4,329 records and 5,882 CDs, but declared he's not sure how or when it got there and stated that he's never listened to it. "Since the comparisons [were made], I really didn't want to get that into it."

Plant, Led Zeppelin bassist John Paul Jones, Spirit bassist Mark Andes and music producer Lou Adler are all expected to take the stand as (and now possibly if?) the trial proceeds over the coming days. Wolfe passed away while saving his son from a riptide near Molokai, Hawaii, on Jan. 2, 1997.

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