When you think about the legendary rock song ‘Stairway to Heaven,’ what comes to mind? Led Zeppelin, of course. However, it’s possible that the band is not the creator of the entire song, and actually took parts of ‘Stairway to Heaven’ from another band. That’s exactly what the estate of the late Randy California (real name – Randy Wolfe), the former lead guitarist of the band Spirit, is attempting to prove.

The lawsuit claims that ‘Stairway to Heaven’ stole the guitar riff at the beginning of the song from one of Spirit’s songs called ‘Taurus.’ For music nerds, the riff consists of a descending chromatic line, which according to the Led Zep defense expert has been around for hundreds of years. Wolfe’s estate claims that Spirit toured with Led Zeppelin in the late 1960s, and that Wolfe even personally taught Led Zeppelin’s Jimmy Page how to play the song ‘Taurus.’

The suit was brought in 2014, but the reason it’s in the news today is that the jury trial for the case began last week in Los Angeles. Thus far, the judge noted that there are certain similarities between the riffs, but that the question of copyright infringement is a question for the jury.

For those of you who aren’t intimately familiar with copyright law, two legal hurdles must be overcome for there to be a finding of illegal copyright infringement First, the plaintiff/claimant (in this case Wolfe’s estate) must show that the defendant(s) had access to the underlying work that is the allegedly infringed work. If the claims in this lawsuit are correct, Led Zeppelin certainly had access to the song. Second, there must be substantial similarity between the two works. Note that under the second factor the works need not be identical – they only need to be substantially similar.  However, bad intent is NOT a prerequisite for a finding of copyright infringement.

The “substantially similar” sounds like a high bar – but in practice it’s more of a loose standard, much like other parts of intellectual property law.  Case decisions are all over the place, depending on the judge/jury and how certain ears interpret the similarity between two songs.

The case is far from over, as the trial resumed today, June 21. Robert Plant, Led Zeppelin’s lead singer, may be called to testify this week. Jimmy Page already testified and claimed that he had never heard the song ‘Taurus,’ despite owning a copy of the album in his vast collection (which he claims he doesn’t know how it got there). John Paul Jones, Zeppelin bassist, testified on Friday, June 17, while Page and Plant looked on. Thus far, it seems like the case has served as a sort of mini-reunion – and so far, the members of Led Zeppelin appear to be on the same side.  This makes a lot of sense, given that millions of dollars in past and future royalties are at stake.

Why this is important:  it remains to been whether Led Zeppelin is as creative as many fans make them out to be – even though they have previously been ordered to pay portions of their royalties for “borrowing” portions of at least two other songs, including ‘Whole Lotta Love’ and ‘Boogie with Stu.’ This case will also shine new light on the “substantial similarity” standard for establishing copyright infringement.  If you are curious about other cases involving copyright infringement of songs, check out the ‘Blurred Lines’ lawsuit between Marvin Gaye and Robin Thicke, and the ‘He’s So Fine’ lawsuit between George Harrison’s ‘My Sweet Lord’ and The Chiffons’ ‘He’s So Fine.’

More to follow as the case concludes later this week or next.