Shuster heirs in 2010, and the court ruled in DC's favor on the grounds that the 1992 agreement with the Shuster heirs barred them from terminating the grant. Under current US copyright law, Superman is due to enter the public domain in 2033. However, this will only apply (at first) to the character as he is depicted in Action Comics #1, which was published in 1938. Versions of him with later developments, such as his power of "heat vision", may persist under copyright until the works they were introduced in enter the public domain themselves. Lois Lane, who also debuted in Action Comics #1, is expected to enter public domain as well in 2033, but supporting characters introduced in later publications, such as Jimmy Olsen and Supergirl, will pass into the public domain at later dates. Captain Marvel Superman's success immediately begat a wave of imitations. The most successful of these at this early age was Captain Marvel, first published by Fawcett Comics in December 1939. Captain Marvel had many similarities to Superman: Herculean strength, invulnerability, the ability to fly, a cape, a secret identity, and a job as a journalist. DC Comics filed a lawsuit against Fawcett Comics for copyright infringement. The trial began in March 1948 after seven years of discovery. The judge ruled that Fawcett had indeed infringed on Superman. However, the judge also found that the copyright notices that appeared with the Superman newspaper strips did not meet the technical standards of the Copyright Act of 1909 and were therefore invalid. Furthermore, since the newspaper strips carried stories adapted from Action Comics, the judge ruled that DC Comics had effectively abandoned the copyright to the Action Comics stories and Superman, and therefore forfeited its right to sue Fawcett for copyright infringement. DC Comics appealed this decision. The appeals court ruled that unintentional mistakes in the copyright notices of the newspaper strips did not invalidate the copyrights. Furthermore, Fawcett knew that DC Comics never intended to abandon the copyrights, and therefore Fawcett's infringement was not an innocent misunderstanding, and therefore Fawcett owed damages to DC Comics. The appeals court remanded the case back to the lower court to determine how much Fawcett owed in damages. At that point, Fawcett Comics decided to settle out of court with DC Comics. Fawcett paid DC Comics $400,000 () and agreed to stop publishing Captain Marvel. The last Captain Marvel story