In forensic science, Locard’s exchange principle forms one of its bedrocks. Formulated by Edmond Locard (1877-1966), the principle is pretty direct: anytime a crime gets committed, an “exchange” takes place, with a criminal leaving some sort of physical evidence behind and taking some sort of evidence with him or her. Through circumspect observation and sound reasoning, the detective can follow the evidence to learn something about the crime, hopefully solving it.
Whether it’s a drop of blood, some soot and gravel, or a thread of hair, something gets left behind or taken away that links the participants to the event, evoking a story from the materiality of what took place. We can never move through the world as ghosts, untouched and untouching. We’re always producing data.