"The claimants' case is now in tatters," said John Baldwin, representing Random House.
Michael Baigent and Richard Leigh sued Random House, publisher of "The Da Vinci Code," claiming Brown "appropriated the architecture" of their 1982 nonfiction work, "The Holy Blood and the Holy Grail."
During three days of testimony that ended Wednesday at London's High Court, Brown acknowledged that he had reworked other writers' material but rejected claims that he copied two authors' work for his novel, which has sold more than 40 million copies worldwide and remains high on best seller lists three years after its publication.
Both books explore theories, dismissed by theologians, that Jesus married Mary Magdalene, the couple had a child and that the bloodline survives.
"It should also be clear that Mr. Brown did not copy ('The Holy Blood and the Holy Grail') as alleged by the claimants," Baldwin said.
"However, even if Mr. Brown had taken these ideas from (the book), the claimants will still fail. The ideas are of too general a nature to be capable of copyright protection. The claimants' claim relates to ideas at a high level of generality, which copyright does not protect."
Baldwin's four-hour closing argument indicated how seriously Random House takes the fundamental issue of copyright law regarding basic issues such as plot, themes, historical information and interpretations used in novels.
Before he addressed the court, Baldwin presented it with a 95-page copy of his closing argument, including 127 footnotes.
Judge Peter Smith, who often questioned Baldwin, said that Baigent and Leigh had been original in their examination of several issues, such as Jesus' bloodline, and they believe that Brown used a substantial part of their themes in "The Da Vinci Code."