"I really don't want to cry," said the British-born author, 42, who added that she was forced to cease progress on a new novel because her concern over this legal matter had "decimated my creative work," reports the BBC.
Rowling also reportedly denied the case was about money and said she considered the prospective volume by author Steve Vander Ark, a librarian, and his publisher, RDR Books, in Muskegon, Mich., "an act of betrayal."
Rowling filed suit earlier this year, claiming that the book is "nothing more than a rearrangement of her own material."
In its defense, RDR Books claims Rowling seeks to "claim a monopoly on the right to publish literary reference guides, and other non-academic research, relating to her own fiction."
The case is scheduled to last most of this week in the New York U.S. District Court, where Judge Robert P. Patterson will conduct the trial without a jury.
A security guard was assigned to watch over Rowling in court – protecting her from the gaze of any hardcore Potter fans.