The character played by Walter Matthau is based on real-life Justice William O. Douglas, who was appointed to the Supreme Court at the age of 40. Douglas was one of the great liberals in High Court history who believed so nearly absolutely in the First Amendment protections of free speech that he did not attend screenings of pornographic films (a plot device in the movie) as he believed that the movies or any form of expression could not be censored under the U.S. Constitution. Thus, he did not need to see the film as he was going to automatically vote against censoring it.
On July 7, 1981, President Reagan announced the appointment of Sandra Day O'Connor to become the first woman on the Supreme Court. Paramount rushed this film, which had been scheduled to open in February 1982, into release in late August 1981 - before O'Connor took her seat on this film's titular date - in order to capitalize on the publicity, as well as to keep the film from looking dated by the time of its release.
In the movie, the character Ruth Loomis tells the Senate Judiciary Committee that she is one year older than the age when Dan Frost was appointed to the Supreme Court. Since the character of Frost is based on William O. Douglas, who was appointed to the Supreme Court at the age of 40, that would make her 41 years old. Jill Clayburgh, who played Loomis, was 37 years old when the movie was released. The U.S. Constitution sets no minimum age for a Supreme Court Justice. The youngest justice ever appointed was Joseph Story, who was 32 years old when he was appointed in 1811. Story is considered one of the greatest justices ever who, along with Chief Justice John Marshall, shaped the High Court.
The original Broadway production of "First Monday in October" by Jerome Lawrence and Robert E. Lee opened at the Majestic Theater in New York on 3rd October 1978 and only ran for about a couple of months, for 79 performances to be exact, until 9th December that year. The stage production starred movie legend Henry Fonda and younger thesp Jane Alexander who was nominated for the 1979 Tony Award for Actress in a Drama.
Actor James Stephens playing Mason Woods was cast in a part similar to his role in the TV series The Paper Chase (1978). Stephens, who plays law clerk Mason Woods to Supreme Court Justice Dan Snow (Walter Matthau), had played a law student on the television show The Paper Chase (1978) during the 1978-1979 television season. Although his character has a different name in this motion picture, the producers undoubtedly wanted to create a sense of verisimilitude and continuity by casting Stephens as a law clerk here, as though he had graduated from law school and moved on to this position.
The title of this film and its' source play, "First Monday in October," is a reference to the traditional first sitting of the Supreme Court of the United States to begin the court's new annual term, beginning after the annual summer recess. The Supreme Court's annual term traditionally runs from the first Monday in October of each year to the last Friday in June of the following year.
The name of the pornographic film was "The Naked Nymphomaniac". This movie, unlike its source stage play, features clips from this fictional adult movie within a movie, which is evidence the Supreme Court is assessing in the film's story.
This movie was made and released about three years after its source play of the same name, by Jerome Lawrence and Robert E. Lee, was first performed on Broadway in 1978. Lee and Lawrence also wrote the screenplay for the film.
Reportedly, actress Jane Fonda turned down the lead role played by Jill Clayburgh because of the part's conservative nature and preferred to do On Golden Pond (1981) instead with her father Henry Fonda. On Golden Pond earned Jane Fonda an Oscar nomination for Best Supporting Actress. Ironically, Henry Fonda originated Walter Matthau's role, as Associate Justice Dan Snow, in the original 1978 Broadway theatrical production.
The airport that Justice Loomis (Jill Clayburgh) flies into when she returns to Orange County, California actually is John Wayne/Orange County Airport as it existed prior to undergoing major improvements in the late 1980s.
The number of people who sit on the United States Supreme Court is nine. In this film, eight of them are men, one is a woman. The film's tagline reflected this by saying, "In the Supreme Court, there are only eight of them against all of her."
Director Ronald Neame is on record as saying the chemistry between Walter Matthau and Jill Clayburgh, whom he thought was 20 years too young for her role, was not good. He has stated that he thought Anne Bancroft would have been perfect.