Recently, Professor Michael Reiss, the head of science at London’s Institute of Education, said that it is becoming more difficult to teach evolution in schools because of the spread of creationism. This is a debate that has long been burning in the US. Earlier this year, a creationist museum opened near Cincinnati, where children in animal skins play amid model dinosaurs, suggesting they once coexisted and that geological science is nonsense.

When a classroom debate becomes a courtroom debate, the law has a solemn responsibility. Schools, after all, are engaged in the mass production of the minds of the future. Evolutionary science was at the heart of one of the most famous cases involving a school curriculum: the “Scopes monkey trial”, which took place in Dayton, Tennessee in 1925 and featured one of America’s most famous lawyers, Clarence Darrow.

The case arose from events stirred by the passing of a law in Tennessee making it illegal for any publicly-funded institution to deny the Bible’s theory of creation and to teach instead that man descended from “a lower order of animals”. The law was promoted by William Jennings Bryan, a lawyer, fundamentalist Christian and former presidential candidate who wanted to banish Darwinism from classrooms.

John Scopes was a biology teacher who taught evolution as part of his lessons at a local school. He set himself up to be prosecuted in protest against the new law. Bryan, having championed the legislation, volunteered to prosecute him. Darrow, an agnostic, liberal, and a famed defence lawyer, represented him.

The trial took place in a sort of carnival atmosphere in July 1925. There were banners in the streets, lemonade stalls, chimpanzees performing in a sideshow. A thousand people, 300 of them standing, packed into the Rhea County Courthouse. Soon after it began, the trial was moved outdoors and the crowd grew to 5,000. It was the first trial attended by radio announcers: they gave live updating broadcasts to listeners. Presiding at the trial was Judge John T Raulston, a conservative Christian. Despite an objection by Darrow, the proceedings were opened with a prayer.

The prosecution’s case was put simply, by showing that Scopes taught the forbidden science. The trial became lively when Darrow began the defence. His first witness was Dr Maynard Metcalf, a zoologist from Johns Hopkins University, who explained the Darwinian theory of evolution. Bryan, following Dr Metcalf’s testimony, expressed his disgust at the notion that man evolved “not even from American monkeys, but Old World monkeys”.

In an extraordinary scene, the defence called the prosecutor himself to give evidence on the witness stand as a bible expert. As a witness, Bryan was asked questions by Darrow about Jonah being swallowed by a whale, Joshua making the sun stand still (how so when the earth moves round the sun?), and the earth being created in one week. Bryan said: “Everything in the Bible should be accepted as it is given there.” He later gave way on some literalist interpretations and stumbled in some of his answers: “I do not think about things I don’t think about.” If the great flood that destroyed all civilisations was in 2348 BC, how did Bryan explain civilisations that traced their history over 5,000 years? One exchange went like this:

DARROW: “Have you ever investigated to find out how long man has been on the earth?”

BRYAN: “I have never found it necessary.”

Eventually, the judge, who had been in church in the front pew when prosecutor Bryan had delivered a sermon on the first Sunday during the trial, stopped Bryan’s evidence and adjourned the hearing. He then ordered Bryan not to return to the stand, and ordered his earlier testimony to be stricken from the record.

At the end of the trial, Darrow asked the jury to return a verdict of guilty so that the case could go to the Tennessee Supreme Court. The jury obliged, and Scopes was fined $100. The conviction, though, was overturned on appeal. Not on the constitutional basis on which Darrow and his team had argued (freedom of expression for science) but because the judge had fixed the $100 fine. According to Tennessee law, since it was over $50 it should have been fixed by the jury.

Clarence Darrow acted in many famous cases. He was notably erudite and committed to defending freedom of expression and opposing the death penalty. In 1926, he won an acquittal for a black family, that of Dr Ossian Sweet, who had resisted a savage racist mob trying to expel them from a white district in Detroit. Darrow, who died in 1938, was a good-hearted man. He defended half his clients free of charge. Wherever possible, though, a fee was as important to him as to any working lawyer. "How can I ever thank you?" gushed a woman to Darrow after he had solved all her legal troubles. "My dear woman," Darrow replied, "ever since the Phoenicians invented money, there has been only one answer to that question."

Professor Gary Slapper is Director of the Centre for Law at The Open University

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