Legendary jack-of-all trades Charlie Chaplin is best known for his childlike Tramp character. But in 1943, Chaplin became embroiled in an adults-only legal drama when his alleged former paramour slapped him with a paternity suit—a case that would change the future of family law in America.

In 1941—while still married to his third wife, Modern Times actress Paulette Goddard—Chaplin met a promising young actress named Joan Berry (née Mary Louise Gribble, a.k.a. Joan Barry) and contracted her for a potential film called Shadows and Substance. According to FBI documents, the two became lovers shortly after their first meeting.

In October 1942, Chaplin invited Berry—who was in Los Angeles—to meet him in Manhattan, and purchased her a train ticket. FBI reports state that while in New York, Berry "attended various parties with Chaplin and it is alleged that he made her available to other individuals for immoral purposes." The latter was a violation of the Mann Act, a.k.a. the White Slave Traffic Act, which states that a person cannot cross state lines to engage in prostitution or immoral behavior.

Two months later, back in Los Angeles, the unstable Berry—who was later arrested for vagrancy—broke into Chaplin’s house, where she brandished a gun. She also claimed that the two were intimate at the time. In court, Berry testified that the two engaged in “four acts of sexual intercourse at or about the date when, in the ordinary course of nature, the child must have been begotten. These acts occurred on the 10th, 23d, 24th and 30th days of December, 1942.”

On October 2, 1943, Berry gave birth to a daughter, Carol Ann. When Chaplin denied paternity, Berry not only accused him of violating the Mann Act—a charge on which he was indicted, then exonerated—but took him to court to prove that he indeed was the father of her child.

Between 1944 and 1945, the Chaplin-Berry scandal unfolded in court. By then, Chaplin was married to his fourth and final wife, Oona O’Neill. (The couple would have eight children together and remain married for more than three decades, until Chaplin’s passing in 1977.)

Back then there was only one method of determining the paternity of a child: a blood test. So blood was drawn from Chaplin, Berry, and baby Carol Ann. Three doctors weighed in on the results, with each one coming to the same conclusion: Chaplin was not the child’s father. Which prompted Berry’s own lawyer to state that “Three distinguished medical men, preeminent in their fields, have decided that Mr. Chaplin is eliminated. We must and do abide by their conclusions.”

But Berry wasn’t done yet.

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Prior to the testing, Berry had signed an agreement with Chaplin saying that if the tests concluded he was not Carol Ann’s father, she would dismiss the charges. When the paternity findings weren’t in her favor, she reneged and pursued Chaplin further.

Though they were the only method of determining paternity at the time, in 1940s California, blood tests weren’t actually admissible in court. So Chaplin had two trials: the first was deadlocked, and in the second one, in April 1945, a jury voted 11 to 1 that he indeed was Carol Ann's father, even though the evidence proved otherwise. Because of the ruling, Chaplin was forced to pay child support and court fees. In 1946 Chaplin appealed the ruling, but lost.

The brouhaha surrounding Chaplin’s case and similar paternity suits (like 1937’s Arais v. Kalensnikoff and 1951’s Hill v. Johnson) led to the reformation of paternity laws in the state of California, with other states eventually following suit. In 1953, along with Oregon and New Hampshire, California drafted the Uniform Act on Blood Tests to Determine Paternity, which in legalese states that: “If the court finds that the conclusions of all the experts as disclosed by the evidence based upon the tests are that the alleged father is not the father of the child, the question of paternity shall be resolved accordingly.”

Though Chaplin’s landmark case continues to help clarify paternity laws today, it was too late for Chaplin, whose popularity was shattered along with his public image. During the course of the suit against him, Chaplin was called everything from a “grey-haired old buzzard” to “a little runt of a Svengali.”

On September 19, 1952, one day after he boarded the Queen Elizabeth with his family in order to attend the world premiere of Limelight in his hometown of London, the U.S. attorney general revoked Chaplin’s reentry permit. Chaplin’s response? “I would not go back there even if Jesus Christ was the president.”

Eventually, Chaplin did return to America, but only on one occasion: to accept an Honorary Oscar in 1972, where he was met with a standing ovation.