From goodpenmanship: Sherlock Holmes provides testimony at a criminal trial.
"Mr. Holmes, what led you to believe that Alec Cunningham was lying about what he had seen?"
Holmes nodded gravely. "The wound upon the dead man was, as I was able to determine with absolute confidence, fired from a revolver at the distance of something over four yards, as there was no powder-blackening on the clothes. Evidently, therefore, Alec Cunningham had lied when he said that the two men were struggling when the shot was fired. Again, both father and son agreed as to the place where the man escaped into the road. At that point, however, as it happens, there is a broadish ditch, moist at the bottom. As there were no indications of boot marks about this ditch, I was absolutely sure not only that the Cunninghams had again lied, but that there had never been any man upon the scene at all."
The barrister scoffed. "You are very confident in your conclusions, Mr. Holmes, but is it not possible that you simply missed boot marks that were indeed present?"
"There is no possibility," said Holmes. "Observation is my trade. From those observations I can build up an absolute chain of reasoning." He studied the barrister for a moment and added. "For example, you, sir,, are a sedentary man who goes out little, uses lime cream in his hair, and has recently lost the regard of his wife."
The courtroom erupted into titters, and the judge was forced to bang upon the bench with his gavel to restore order.
"I resent the implication about my wife," the barrister sputtered. "I will ask you to refrain from these scurrilous attempts to distract the jury from the case at hand."
"The announcement of your marriage appeared in the newspaper some months ago," Holmes interrupted. "Yet for the past three weeks, during which I have frequently testified in court, I have observed that the powder in your wig has been applied haphazardly. It is unlikely that the lady has been from home for so long, as you lack the money to hire more than a single servant. Despite her presence at home, she has allowed you to go out in such a disreputable condition. It is clear that she no longer holds the same regard for you as she did formally. Moreover, given the lady's evident disdain, it is very unlikely that she is responsible for the three strands of long blond hair currently clinging to your shoulder."
Up in the observation area, I could not contain my smile. The barrister, however, flushed bright red.
"No...no further questions, Your Honor," he managed.
Holmes nodded his head at the unfortunate barrister and stepped down lightly from the witness box.
A/N: Holmes' explanation is copied directly from The Adventure of the Reigate Squire, while I based his observations of the unfortunate barrister on those in The Adventure of the Blue Carbuncle. It's hard to come up with deductions!
