From dry mouths and Song dynasty flies to arsenic tests in the courtroom
In ancient India, some accused people were handed a mouthful of dry rice and told to spit it back. The idea had a grain of logic: fear dries up saliva, so a guilty person might struggle. Crude as it was, the trick foreshadowed the polygraph and belongs to the long prehistory of forensic science.
The word forensic comes from the Latin forensis, meaning of the forum, because Roman trials and preliminary hearings took place in that public square. That origin explains its two modern senses, legal evidence and public speaking. Today forensic scientists gather, preserve and analyse evidence at scenes or in laboratories, study DNA, fingerprints, toxicology and fire debris, examine financial records, and testify as expert witnesses for either prosecution or defence.
Ancient justice leaned heavily on witnesses and forced confessions, though hints of method appear. In China, a variant of the rice test used rice powder, and in 1248 the Song dynasty official Song Ci wrote Washing Away of Wrongs, the earliest known written account of using medicine and entomology to solve crimes. He set rules for reporting examinations to court, stressed that investigators must be seen as impartial, and estimated time of death with allowances for weather and insects. One case in his book was cracked when flies settled on a single farm sickle among many collected from suspects.
European practice sharpened later. Sixteenth-century army and university doctors began recording causes of death, and the Italian surgeons Fortunato Fidelis and Paolo Zacchia laid groundwork for modern pathology by studying how disease alters the body. The Enlightenment curtailed torture as a route to confession and pushed witchcraft out of courtrooms. In 1816 at Warwick, investigators matched a corduroy imprint with a sewn patch, plus scattered wheat and chaff, to the breeches of a labourer who had been threshing nearby.
Chemistry followed. Swedish chemist Carl Wilhelm Scheele found a way to detect arsenious oxide in 1773, and in 1806 Valentin Ross extended it to stomach tissue. When James Marsh testified in 1832 that coffee in a poisoning trial held arsenic, his yellow precipitate had decayed by the time jurors saw it, and the defendant John Bodle was acquitted on reasonable doubt. By 1885 Scientific American reported microscopes telling two people's blood apart in a Chicago case, and gas chromatography with mass spectrometry now identifies drugs and accelerants in trace amounts.
Source: Forensic science
