One of the standard tropes in science fiction is some kind of device that can render someone unconscious — you know, like a phaser set to stun. We can imagine times when being aggressively knocked out would lead to some grave consequences, but — we admit — it is probably better than getting shot. However, we don’t really have any reliable technology to do that today. However, if you’ve passed a modern-day policeman, you’ve probably noticed the Taser on their belt. While this sounds like a phaser, it really isn’t anything like it. It is essentially a stun gun with a long reach thanks to a wire with a dart on the end that shoots out of the gun-like device and shocks the target at a distance. Civilian Tasers have a 15-foot long wire, while law enforcement can get longer wires. But did you know that modern Tasers also fire confetti?

It sounds crazy, and it isn’t celebratory. The company that makes the Taser — formerly, the Taser company but now Axon — added the feature because of a common complaint law enforcement had with the device. Interestingly, many things that might be used in comitting a crime are well-understood. Ballistics can often identify that a bullet did or did not come from a particular weapon, for example. Blood and DNA on a scene can provide important clues. Even typewriters and computer printers can be identified by variations in their printing. But if you fire a taser, there’s generally little evidence left behind.

Well, that was true until the AFIDs (Anti Felony Identification) came on the scene in 1993. The Taser uses a cartridge that has one or more spools of wire. When you fire the unit, you remove the cartridge and replace it with a new one. The cartridge also has some kind of propellant that fires the dart and wire. Early cartridges used gunpowder, although the newer ones appear to utilize gas capsules. The wire moves between 180 and 205 feet per second. But modern ones also have a few dozen very small disks inside that spew out under the force of the propellant. Each tag has a unique serial number for that cartridge.

Sure, if you have time, you could sweep up the 20 or 30 little tags. But they are less than a quarter of an inch around and disperse widely. Plus, you can’t be sure exactly how many tags are in any given cartridge, so you’d have to be very thorough. In fact, it is hard enough for investigators to find them when they want to. The tags are colorful and show up better when using special lights.

This isn’t just theoretical, by the way. Milwaukee police used AFIDs to track down a thief who stunned a musician and made off with a 300-year-old Stradivarius violin worth about $5 million. In another case, a man did extensive research about killing his boss to avoid being caught embezzling. He used a Taser to subdue his victim and knew to vacuum up the AFIDs, but didn’t get them all, allowing police to identify him as the killer.

Some printers and copiers leave digital fingerprints, too. On the other hand, some people seem to enjoy getting the occasional jolt of voltage.