In an era when eyewitness testimony and “smoking gun” evidence were needed to convict and police incompetence meant that Jack the Ripper stalked the streets freely, Sherlock Holmes used chemistry, bloodstains and fingerprints to catch offenders. In many ways, the modern detective can be seen as a direct extension of Conan Doyle’s literary genius. Using interviews and archival materials, "How Sherlock Changed the World" explores real crimes that were solved thanks to techniques, equipment or methods of reasoning Holmes used.

Forensic scientist Dr. Henry Lee shows how he used blood evidence to free a woman charged with the murder of her husband in a mysterious case in Florida, and Karen Smith demonstrates how blood splatter patterns exonerated Dr. Sam Sheppard of his wife’s murder years after his conviction. The history of Sherlock’s techniques from the 1880s to the present is explored, showing how the scientific methods he introduced to the world have evolved into the stunning CSI-style forensic labs of Scotland Yard and the FBI.

Holmes was the first to use ballistics as evidence in criminal cases. Long before modern toxicologists developed sophisticated tests for chemical analysis, Holmes was using scientific methods to detect the presence of poisons. Forensic Scientist Edmond Locard built the first real forensics lab in 1910, 23 years after Sir Arthur Conan Doyle dreamed up a fictional one. Like Sherlock, Locard kept meticulous collections of soil, mineral, fiber and hair samples and used a microscope to identify trace evidence.

The film demonstrates that the legacy of Holmes is not solely as a reservoir of brilliant stories and wonderfully drawn characters, but can be found in the development of modern scientific criminal investigation techniques and improved methods for capturing today’s criminals.