Re:Why not take your DNA? (Score 1)

The issue isn't whether or not the store has your precious fingerprint; indeed, you left several on the cheque you handed the cashier, dozens more on the handle of the shopping cart, and if you borrowed the pen . . .

To put it simply: the store already has a copy of your grimey finger prints, albeit a latent copy. They probably have some of your DNA thanks to a few hair fibers you likely shed while waiting in the check-out line.

The stores worried about forged cheques are going to demand to see your valid driver's license -- probably even recording the number on the front of the cheque. They will likely verify that the address on the license matches the info printed on the front of your friggin' cheque! How private do you think you can be when you're handing out pre-printed forms that contain you name, address and phone number on them (not to mention your signature on the bottom).

In other words, they know exactly who you are. More accurately, they know whom you purport to be.

This is an issue about authentication and non-repudiation. I wonder if the problem is with forged cheques a la identity theft (where the thumbprint would be useful in finding the identity of the Bad Guy), or is it with people claiming to have been the victim of someone forging their names when it wasn't an imposter at all.

If the more common problem is the latter, then the thumbprint serves as a useful tool to ensure non-repudiation. If it's your thumbprint -- something easily determined when testing against a "known good" sample (your thumb) -- then you wrote the cheque, even if you did sign it with a crayon.