Smash and grab

I normally write about inventions that are tangible things, but an item in today's free Metro newspaper caught my eye.

It is about a product that the newspaper calls SmartWater, but which is more correctly called SmartWater® as it has been registered as a trade mark by Smartwater Limited, a company based in Walsall. The item shows a "hoodie" glaring at the photographer, hands in pockets, with glowing green stains on his pink jacket.

The product is a substance that, when sprayed onto robbers of cash delivery vans, shows up when viewed under ultraviolet light. This could be evidence for conviction. As I read the short piece, I thought to myself that if the composition had a unique combination of chemicals then it would not just provide grounds for suspicion, but would directly tie the jacket to the scene of the crime.

I believe that the relevant invention is Improvement in security systems . It suggests using coumarin derivatives but the real point of the patent is using unique combinations of trace chemicals that can be digitally analysed: just what I had thought, and just what the writer of the piece had missed. Please excuse a little bit of schadenfreude.

In my last book, Inventing the American Dream, I wrote about the idea of exploding packs of cash in the chapter on crime. Dye coming out of cash packs dates back at least to US 3053416 in 1960, where the teller had to push a button to release it. The problem with that, apparently, was that the robbers would go wild in the banking hall as the packs exploded in their hands. To prevent the resulting shootouts, later inventions such as US 3564525 provided for electromagnetic gates at the doorways that would trigger the packs after a time delay.

It occurs to me that an even better use of the Smartwater product would be if the spray was subtle, as if water had accidentally been released, rather than obvious. Apparently G4S is today to be the first company to use the product.