Final answer:
The judge in the Scopes Trial made a critical decision to exclude expert testimony on evolution, thereby focusing the trial on John Scopes's violation of the law rather than the scientific validity of evolution. This shifted the trial to highlight cultural conflicts between secular and religious values.
Step-by-step explanation:
A key decision by the judge during the Scopes Trial was to disallow experts from testifying on the validity of the theory of evolution. This decision was crucial because it effectively prevented the defense from arguing that the law Scopes was accused of violating was itself invalid because it prohibited the teaching of a scientifically accepted theory. Instead, the trial focused more on the defendant's violation of the law and the cultural conflict between modern liberal values and conservative Christian fundamentalism.
During the trial, the dramatic highlight emerged when Clarence Darrow, leading the defense, called William Jennings Bryan, who represented the prosecution, to the stand as an expert witness on the Bible. Darrow's intense cross-examination led to a moment where Bryan admitted that not all biblical passages should be taken literally, which for many debunked the prosecution's fundamentalist stance. Although the trial ended with John Scopes being found guilty, the broader impact on American society and the clash between secular and religious ideologies remained significant.