Louis J. Marcone came up with a novel way to catch bank robbers in 1989: The teller might step on a trigger and surreptitiously spray the robber with “a non-toxic, clear, odorless and harmless liquid spray material which can be readily detected by trained police dogs.”

He envisioned a second application for the device: The spray unit could be attached to a fire alarm, so that anyone who pulled the alarm would be marked with the scent. “If the alarm was determined to be a false alarm, the fire department can alert police to bring trained police dogs to the scene, whereupon the dog can track the scent from the alarm location to the person activating the false alarm.”