LOS ANGELES (Reuters) - Jurors in Led Zeppelin's copyright infringement trial were due to begin a second day of deliberations on Thursday to decide whether the English rock band ripped off the opening chords of "Stairway to Heaven" from an American group.

The trial in U.S. District Court in Los Angeles has called into question the originality of the signature song of one of the top-selling rock acts of all time.

The lawsuit was brought in 2014 by Michael Skidmore, a trustee for the estate of the late Spirit guitarist and songwriter Randy Wolfe. It accuses Led Zeppelin of copying the opening riff to "Stairway to Heaven" from Spirit's 1967 instrumental "Taurus."

The trial started on June 14, and Led Zeppelin lead singer Robert Plant and guitarist Jimmy Page testified that they were largely unfamiliar with Spirit's music.

In closing arguments on Wednesday, Skidmore's attorney Francis Malofiy argued that Wolfe, who drowned in 1997, is owed a writing credit and that the trust set up in his name should receive millions of dollars in damages.

Led Zeppelin's attorney Peter Anderson told jurors the riff in question, a chromatic descending arpeggiated line that misses the "E" note, was in the public domain and had been widely used.

Skidmore can only seek damages starting from 2011, based on a three-year statute of limitations set by U.S. copyright law, according to court papers.

Judge Gary Klausner ruled that jurors must decide the case by relying on the sheet music for the two songs and cannot listen to Spirit's recording of "Taurus."

Outside of court on Wednesday, Malofiy told reporters that the ruling presented an obstacle for his side.

Led Zeppelin broke up in 1980.

(Reporting by Alex Dobuzinskis; Editing by Leslie Adler)