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Swedish chemist Carl Wilhelm Scheele devolved the first chemical test for arsenic, which involved changing arsenic trioxide to garlic-smelling gas using nitric acid and zinc. This was the first chemical test capable of detecting arsenic in a corpse
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A comparison of bullets was made for the first time in a criminal investigation by Henry Goddard. He found a unique defect on a bullet recovered from a crime scene that exactly matched a corresponding mark on the bullet mold from a suspect's home
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The presumptive blood test was based on the discovery by Christian Friedrich Schöbein that hemoglobin in blood causes hydrogen peroxide to foam. This was the first test for blood, which involved applying hydrogen peroxide to a stain to see if it would react and foam, indicating the likely presence of blood