"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."
The issue, Smith said, is whether that amounted to a copyright violation.
If Baigent and Leigh succeed in securing an injunction to bar the use of their material, they could hold up the scheduled May 19 film release of "The Da Vinci Code," starring Tom Hanks. Sony Pictures has said it planned to release the movie as scheduled.
Brown has acknowledged that he and his wife, Blythe Brown, read "The Holy Blood and the Holy Grail" while researching "The Da Vinci Code," but said they also used 38 other books and hundreds of documents, and that the British authors' book was not crucial to their work.
Brown testified Wednesday that he was certain he and his wife, who conducts much of his research, had read Baigent and Leigh's book only after he had submitted his synopsis for the manuscript that would become "The Da Vinci Code" to his agent in January 2001.
Asked about passages from "The Da Vinci Code" that were similar to those in "The Holy Blood and the Holy Grail," Brown acknowledged "reworking of the passage, that's how you incorporate research into a novel."
But Brown, who traveled from his New Hampshire home for the trial,.
"I'm not crazy about the word 'copied,'" Brown testified. "Copying implies it is identical. It's not identical."
Brown said "The Holy Blood and the Holy Grail" was "one of the books in the mix" when he and his wife, Blythe Brown, were researching the novel.
The author did not attend Friday's court session.
Random House lawyers argue that the ideas in dispute are so general that they are not protected by copyright. They also say many of the ideas in "The Holy Blood and the Holy Grail" do not feature in Brown's novel, which follows fictional professor Robert Langdon as he investigates the murder of an elderly member of an ancient society that guards dark secrets about the story of Jesus and the quest for the Holy Grail.
The prosecution will present its closing argument Monday, with a verdict possible next week.