The Harry Potter fan behind an unauthorized encyclopedic guide of the hit series broke down on the witness stand in Manhattan on Tuesday.

Steven Vander Ark, the man behind the popular fan site Harry Potter Lexicon, testified on Tuesday in the suit brought last year by author J.K. Rowling and Warner Bros., the studio behind the Harry Potter movies and rights holder of all intellectual property related to the franchise.

Vander Ark became emotional when asked to speak about what the case has done to his reputation in the greater community of Potter fans worldwide.

"It's been difficult because there has been a lot of criticism, obviously, and that was never the intention," he said, stammering and wiping away tears.

"This has been an important part of my life for the last nine years or so."

The former school librarian discovered J.K. Rowling's books and started his website in the late 1990s. He has spent close to a decade studying, discussing and posting information about the novels on his site, of which Rowling herself has admitted to being a fan in the past.

However, his decision to turn parts of his site into book form — to be published by Michigan-based RDR Books — has drawn fire from the powerful author, who is attempting to block the book's publication.

Vander Ark acknowledged on Tuesday that he had been worried that publishing the book would infringe on Rowling's copyright.

He testified that RDR representatives talked him into writing it. The publisher's lawyers have argued that the book should be considered a scholarly reference guide to Rowling's vastly detailed novels and, as such, should be considered fair use.

Rowling took the stand on Monday and criticized the book as "wholesale theft of 17 years of my hard work."

She also said that the proceedings have "decimated [her] creative work" on a new novel and possibly on a Potter encyclopedia, with proceeds earmarked for charity, that she had already started as well.

Rowling fought back tears on Monday as she described how much her books, the characters and the world she created mean to her. Though now wealthy, she began writing the stories when she was an impoverished single mother living on welfare.

"I really don't want to cry because I'm British, you know," she told the federal court.

"These books, they saved me, not just in the very obvious material sense, although they did do that … I would have to say that there was a time when they saved my sanity."

With files from the Associated Press