Clean hand identifier

Okay this is my first post, "Please be gentle" I went to a local restaurant yesterday and quickly dismissed eating there. The cook was in the bathroom stall next to me, and as he left he took a piece of paper towel, blew his nose, tossed it in the trash, and proceeded to walk out of the room without washing his hands. NO HAND WASHING, NOTHING! He didn't even look at the sink! As I hastilly left the diner after letting the manager know, I had a brainstorm. This is what I came up with. There is a thing called "Biometric identification". I suggest we take this one step further, and have the scanner which you stick your hand in identify if your hand has been thoroughly washed.We can use this technology to see the dirt and germs on the human hand. This in combination with an automatic door lock that only unlocks when the clean hand is inserted in the identification area, and is clean, will keep the usual unclean suspect from leaving the bathroom with out clean hands.