(NYTIMES) - One of the year's most anticipated Broadway plays - the screenwriter Aaron Sorkin's adaptation of Harper Lee's novel To Kill A Mockingbird - faces a legal challenge from Lee's estate, which is suing over Sorkin's version of the story.

In a complaint filed Tuesday (March 13) in federal court in Alabama, the estate argued that Sorkin's adaptation deviates too much from the novel, and violates a contract, between Lee and the producers, which stipulates that the characters and plot must remain faithful to the spirit of the book.

A chief dispute in the complaint is the assertion that Sorkin's portrayal of the much beloved Atticus Finch, the crusading lawyer who represents a black man unjustly accused of rape, presents him as a man who begins the drama as a naive apologist for the racial status quo, a depiction at odds with his purely heroic image in the novel.

In February, the lawsuit says, Tonja B. Carter, the lawyer Lee appointed to run her estate, met with Scott Rudin, a producer of the play, for one to two hours to express "serious concerns about the script". "At times, the conversation was heated," but the meeting ended without a resolution, the lawsuit said.

The contract the parties signed states that "the Play shall not derogate or depart in any manner from the spirit of the Novel nor alter its characters". The Rudin team is arguing it does not, and that, while the producers must listen to the estate's view, they are the final arbiters of whether the production is faithful to the novel.

"I can't and won't present a play that feels like it was written in the year the book was written in terms of its racial politics: It wouldn't be of interest," Rudin said in an interview. "The world has changed since then."

The play, which is scheduled to begin previews Nov 1 and to open Dec 13 on Broadway, is a joint production of Rudin and Lincoln Center Theater. A lawyer who filed the lawsuit for Lee's estate, Matthew H. Lembke, declined to comment.

The cast is led by Jeff Daniels, as Atticus, and includes Celia Keenan-Bolger as his daughter Scout, Will Pullen as her brother Jem and Gideon Glick as their friend Dill. Casting for the role of Arthur (Boo) Radley has not yet been announced. Rudin said he was surprised by the estate's criticism of Sorkin's depiction of Atticus because Carter had been instrumental in the 2015 publication of Go Set A Watchman, an early draft of Mockingbird that depicted an aged Atticus as a racist and segregationist. The lawsuit states that the play should not deviate from the depiction of Atticus in Mockingbird, where he is presented as a defender of racial equality in a divided south.

"Based on Ms. Lee's own father, a small-town Alabama lawyer who represented black defendants in a criminal trial, Atticus Finch is portrayed in the novel as a model of wisdom, integrity, and professionalism," the suit says.

Lee signed the contract authorising the play in June 2015, eight months before she died at age 89. She received US$100,000 (S$131,000) for the production rights, as well as what Broadway experts described as a generous portion of the box office revenue and any net profit.

The dispute erupted last fall when Carter saw a draft of the script, and was alarmed by what she viewed as liberties taken with the source material. The suit cites an interview Sorkin did last fall where he described how Atticus evolves over the course of the play, in part through his interactions with the Finch family's black maid, Calpurnia, who has a much larger role in the drama.

Carter was also troubled by the addition of two characters who do not appear in the book, and by what the complaint describes as changes to the characters of Atticus' children, Jem and Scout.

In the interview Sorkin gave New York Magazine about his adaptation, he described his reinterpretation of Atticus' moral evolution. "As far as Atticus and his virtue goes, this is a different take on Mockingbird than Harper Lee's or Horton Foote's," he said. "He becomes Atticus Finch by the end of the play."

The move to assert more control over the play is perhaps a sign of how Carter views her role as a guardian of Lee's legacy. In her final years, Lee went to court to protect her intellectual property, and sued a museum in her hometown, Monroeville, in 2013, arguing that it had infringed on Lee's trademark by selling Mockingbird themed T-shirts and trinkets (the suit was settled in 2014).

Rudin alluded to that lawsuit in a statement that said the "estate has an unfortunate history of litigious behaviour and of both filing and being the recipient of numerous lawsuits, and has been the subject of considerable controversy based on the perceptions surrounding its handling of the work of Harper Lee both before and after her death".

"This is, unfortunately," the statement continued, "simply another such lawsuit, the latest of many, and we believe that it is without merit. While we hope this gets resolved, if it does not, the suit will be vigorously defended."