An arsonist who set Washington on fire in 1985 (2007)
alternet.org
alternet.org
"Investigators knew from the bags left behind at the fire scenes that the arsonist shopped at convenience stores. From the wreckage of a Northeast car fire investigators pulled the remnants of a black plastic bag. The company supplied their black bags to just two shops in the D.C. area. Investigators put cameras in both stores.
With the cooperation of the owner of the two Circle 7 stores, agents affixed thumbnail-size stainless steel chips to the bottom of every bag in both stores. Each chip was marked according to alphanumeric code, going in order through the stack. If one of the bags were to be involved in a fire, the chip would survive. And because agents went to the stores daily to track which bags had been used, they would be able to go to the video to see which customer had purchased the bag from the fire."
The above was not how the arsonist was caught. (He was caught due to his car being captured on video leaving the scene of a fire. Having found a suspect, the investigators matched his DNA to DNA extracted from clothing he'd used as wicks in setting some of the fires.)