Throughout most of history, criminal convictions required either a confession by the accused or the testimony of at least two witnesses. There were a few occasions when physical evidence was used. The first such documented case appears in a Chinese book written in 1247. The book is a guidebook for coroners; it touches upon some issues related to murder. For example, it notes that strangulation can be detected by examining the delicate bones in the neck for damage. Its most famous case arose from a clever ploy to expose a murderer. As translated by Brian McKnight:
A local peasant from a Chinese village was found murdered, hacked to death by a hand sickle. The use of a sickle, a tool used by peasants to cut the rice at harvest time, suggested that another local peasant worker had committed the murder. The local magistrate began the investigation by calling all the local peasants who could be suspects into the village square. Each was to carry their hand sickles to the town square with them. Once assembled, the magistrate ordered the ten-or-so suspects to place their hand sickles on the ground in front of them and then step back a few yards. The afternoon sun was warm and as the villagers, suspects, and magistrates waited, bright shiny metallic green flies began to buzz around them in the village square. The shiny metallic colored flies then began to focus in on one of the hand sickles lying on the ground. Within just a few minutes many had landed on the hand sickle and were crawling over it with interest. None of the other hand sickles had attracted any of these pretty flies. The owner of the tool became very nervous, and it was only a few more moments before all those in the village knew who the murderer was. With head hung in shame and pleading for mercy, the magistrate led the murderer away. The witnesses of the murder were the brightly metallic colored flies known as the blow flies which had been attracted to the remaining bits of soft tissue, blood, bone and hair which had stuck to the hand sickle after the murder was committed. The knowledge of the village magistrate as to a specific insect group’s behavior regarding their attraction to dead human tissue was the key to solving this violent act and justice was served in ancient China.
The use of physical evidence in criminal cases did not become common until early in the nineteenth century. An early case in 1794 was serendipitous. A burglar in England shot and killed Edward Culshaw. The coroner removed the bullet from the victim’s head and discovered along with it the paper wadding. Back then, you loaded a pistol or musket by pouring in some gunpowder, then pushing the ball down to the gunpowder, and lastly stuffing some paper down the muzzle to hold everything in place so that it wouldn’t fall out. When the gun was fired, the paper wadding was pushed into the victim’s skull by the ball. The physician retrieved that paper and was able to read it well enough to determine that it came from a sheet of music. The investigators arrested a suspect and discovered the matching sheet of music in the suspect’s pocket. This evidence was sufficient to convict the murderer.
A variety of other advances offered other avenues of physical proof. Chemists developed tests for arsenic, leading to convictions of poisoners. Police learned to examine bullets recovered from victims for unique marks that could be matched to the guns of suspects. Sir William Herschel (not the astronomer) started using fingerprints for purposes of identification in 1858. The idea spread and was further developed by other people. Mark Twain was fascinated by this idea and referred to it in his 1883 book, Life on the Mississippi. In his 1894 novel Pudd’nhead Wilson, a brilliant piece on the idiocies of racism, Twain used fingerprinting as a crucial plot device. By 1900 fingerprinting was broadly acknowledged as a reliable means of identifying people. The science of forensics was recognized as an important tool in the fight against crime, and steadily grew in importance.
This tells us much about the degree of rationalism common in Western nations. The notion that physical evidence could prove guilt did not command much credence until after 1800. But by 1840 the idea was so well-admired that Edgar Allen Poe crystallized it with the first detective stories ever published: The Murders in the Rue Morgue, The Mystery of Marie Roget, and The Purloined Letter. In each of these stories, the detective, Mr. C. Auguste Dupin, solves the crime by careful examination of physical evidence. Interestingly, the word “detective” did not enter common parlance until about 1860; here’s the Google NGram chart for the frequency of occurrence of the word in English literature:
The skilled interpretation of physical evidence seized the public imagination, and detective stories quickly became so popular that Mark Twain satirized the genre with Tom Sawyer, Detective. Nowadays detective stories are a major part of entertainment.