Although Locard's exchange principle is generally understood as the phrase "with contact between two items, there will be an exchange," Edmond Locard never actually wrote down those words in the vast amount of material he produced, nor did he mention anything concerning a principle. Locard, however, did write the following:
"It is impossible for a criminal to act, especially considering the intensity of a crime, without leaving traces of this presence."
John Fuller "How Locard's Exchange Principle Works" 1 January 1970. HowStuffWorks.com. <https://science.howstuffworks.com/locards-exchange-principle.htm> 6 October 2024