LONDON – Like a good thriller, “The Da Vinci Code” trial has had drama, controversy and conflict. And it’s ending with a cliffhanger – which way will a judge rule in the copyright infringement case against the publisher of Dan Brown’s world-conquering novel?

High Court justice Peter Smith rules Friday in the claim by authors Michael Baigent and Richard Leigh against “Da Vinci Code” publisher Random House.

Smith must decide whether Brown’s blockbuster “appropriated the architecture” of Baigent and Leigh’s 1982 nonfiction book, “The Holy Blood and the Holy Grail.” In the United States, the book is titled, “Holy Blood, Holy Grail.”

Both books explore theories that Jesus married Mary Magdalene, the couple had a child and the bloodline survives.

Most historians and theologians scoff at such ideas, but Brown’s fast-paced mix of murder, mysticism, code-breaking and art history has won millions of fans.

“The Da Vinci Code” has sold more than 40 million copies – including 12 million hardcovers in the United States – since it was released in March 2003. It came out in paperback in the United States last week, and quickly sold more than 500,000 copies, an astonishing pace for a paperback release. An initial print run of 5 million has already been raised to 6 million.

A victory by Baigent and Leigh would stun the world of copyright law, challenging the concept that copyright protects the expression of an idea rather than the idea itself.

“A victory for Leigh and Baigent would make it very difficult for novelists, particularly historical novelists,” said Fiona Crawley, a copyright expert with law firm Bryan Cave LLP.

“They go to source books to research the history to incorporate into their novel. It would call into question how they can research a historical novel without being accused of copyright infringement by the historian who has written the key work on that incident in history.”

A win by the plaintiffs also could hold up the scheduled May 19 film release of “The Da Vinci Code” movie, starring Tom Hanks. Sony Pictures says it plans to release the film as scheduled.

If Leigh and Baigent lose, they could have to pay costs that legal experts estimate will top $1.75 million.