When Lincoln was a young man living in New Salem, Illinois, a local bully, Jack Armstrong, challenged Lincoln to a wrestling match. Lincoln won, and earned Armstrong’s respect and friendship.
Twenty years later, in 1857, Lincoln learned that Jack’s son William, nicknamed Duff, had been charged with murder. Jack was now dead, and Lincoln wrote to his widow, Hannah, offering to defend Duff at no charge.
Lincoln traveled to Beardstown, Illinois for the trial. The prosecution’s case rested on the testimony of key witness Charles Allen, who claimed he had seen Duff Armstrong perform the murder.
On cross-examination, Lincoln asked Allen about the precise details of what happened that night. Allen testified that on August 29, 1857, at approximately 11:00 p.m., there was a full moon and that from a distance of about 150 feet he saw Armstrong strike the lethal blow.
Lincoln asked the judge for permission to enter an 1857 almanac into evidence. This was not a common trial technique at that time, because the judicial system relied almost entirely on witness testimony.
Lincoln asked Allen to read the almanac entry for August 29, 1857. There was no full moon that night; in fact, there had been no moon at all by 11:00 o’clock. Therefore, it would have been impossible for Allen to see anything from a distance of 150 feet. Lincoln had successfully discredited the witness.
Armstrong’s trial was over by the end of the day. After only one ballot, the jury found Armstrong was not guilty.